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{{short description|1938 fighter aircraft family by Bell}}
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{{Infobox aircraft
 |name = P-39 Airacobra
 |image = File:P-39N Airacobra of the 357th Fighter Group at Hamilton Field in July 1943.jpg
 |caption = P-39Q ''Saga Boy II'' of Lt. Col. Edwin S. Chickering, CO [[357th Fighter Group]], July 1943
 |type = [[Fighter aircraft|Fighter]]
 |manufacturer = [[Bell Aircraft]]
 |national_origin= United States
 |first_flight = 6 April 1938<ref name="Angelucci and Bowers p.41">Angelucci and Bowers 1987, p. 41.</ref>{{refn|Some sources give 6 April 1939 as the date of the first flight; there is very good evidence that 1938 is correct (see talk page).<ref name=Matthews85>Matthews 1996, p. 85.</ref>|group=N}} 
 |introduction = 1941
 |status = Retired
 |primary_user = [[United States Army Air Forces]]
 |more_users = [[Soviet Air Force]]<br/>[[Royal Air Force]]
 |produced = 1940 – May 1944
 |number_built = 9,588<ref>{{cite book|last=Angelucci|first=Enzo|title=Combat aircraft of World War II|year=1988|page=40|publisher=Orion Books |isbn=0-517-64179-8}}</ref>
 |variants = [[Bell XFL Airabonita]]<br/>[[Bell P-76]]
 |developed_into = [[Bell P-63 Kingcobra]]
}}

The '''Bell P-39 Airacobra''' is a [[fighter aircraft|fighter]] produced by [[Bell Aircraft]] for the [[United States Army Air Forces]] during [[World War II]]. It was one of the principal American fighters in service when the United States entered combat. The P-39 was used by the [[Soviet Air Force]], which used it to score the highest number of kills attributed to any US fighter type flown by any air force in any conflict.{{refn| The P-39 has the highest total number of individual victories attributed to any US fighter type, not kill ratio; Finnish-modified [[Brewster F2A Buffalo|Brewster Buffalos]] had the highest kill ratio.|group=N}} Other major users of the type included the [[Free French]], the [[Royal Air Force]], and the [[Italian Co-Belligerent Air Force]].<ref name="Gunston p. 22">Gunston 1980, p. 22.</ref>

The P-39 had an unusual layout, with the engine installed in the center fuselage behind the pilot, and driving a [[tractor propeller]] in the nose via a long shaft. It was also the first fighter fitted with a [[tricycle undercarriage]].<ref name= " Angelucci and Matricardi p. 25.">Angelucci and Matricardi  1978, p. 25.</ref>  Although the mid-engine placement was innovative, the P-39 design was handicapped by the absence of an efficient [[turbocharger|turbo-supercharger]], preventing it from performing well at high altitude. For this reason it was rejected by the RAF for use over western Europe but adopted by the USSR, where most air combat took place at medium and lower altitudes.

Together with the derivative [[Bell P-63 Kingcobra|P-63 Kingcobra]], the P-39 was one of the most successful fixed-wing aircraft manufactured by Bell.<ref>Bishop, Chris. ''The Encyclopedia of Weapons of World War II''. New York: Orbis Publishing Ltd., 1998. {{ISBN|0-7607-1022-8}}.</ref>

==Design and development==

===Circular Proposal X-609===

In February 1937, Lieutenant [[Benjamin S. Kelsey]], Project Officer for Fighters at the [[United States Army Air Corps]] (USAAC), and Captain [[Gordon P. Saville]], fighter tactics instructor at the [[Air Corps Tactical School]], issued a specification for a new fighter via ''Circular Proposal X-609''.<ref>Bodie 1991, p. 19.</ref> It was a request for a single-engine high-altitude "[[Interceptor aircraft|interceptor]]" having "the tactical mission of interception and attack of hostile aircraft at high altitude".<ref>Bodie 1991, pp. 16–17.</ref> Despite being called an interceptor, the proposed aircraft's role was simply an extension of the traditional [[Fighter aircraft#World War I|pursuit (fighter)]] role, using a heavier and more powerful aircraft at higher altitude. Specifications called for at least {{cvt|1000|lb}} of heavy armament including a cannon, a liquid-cooled Allison engine with a [[General Electric]] [[turbocharger|turbo-supercharger]], [[tricycle undercarriage|tricycle landing gear]], a level airspeed of at least {{cvt|360|mph|km/h kn}} at altitude, and a climb to {{cvt|20000|ft|-3}} within six minutes.<ref name="Dave's">''[http://www.daveswarbirds.com/usplanes/aircraft/histp-38.htm Lockheed P-38 Lightning]''. Retrieved: 21 January 2007.</ref> This was the most demanding set of fighter specifications the USAAC had presented to that date.{{refn|Brigadier General [[Benjamin S. Kelsey]] recalled in 1977 he and Lieutenant [[Gordon P. Saville]] (later General) drew up the specification in 1937 using the word "interceptor" as a way to bypass the inflexible Army Air Corps requirement for pursuit aircraft to carry no more than {{cvt|500|lb}} of armament including ammunition. Kelsey was looking for a minimum of {{cvt|1000|lb}} of armament.<ref>Bodie 1991, p. 14.</ref>|group=N}} Although Bell's limited fighter design work had previously resulted in the unusual [[Bell YFM-1 Airacuda]], the ''Model 12''<ref name= "Donald p. 106">Donald 1997, p. 106.</ref> proposal adopted an equally original configuration with an [[Allison V-1710|Allison V-12]] engine mounted in the middle of the [[fuselage]], just behind the cockpit, and a propeller driven by a shaft passing beneath the pilot's feet under the cockpit floor.<ref name= "Donald p. 106"/>

[[File:Bell XP-39.jpg|thumb|Bell XP-39 showing the position of the supercharger air intake]]

The main purpose of this configuration was to free up space for a 37&nbsp;mm [[Browning Arms Company]] [[M4 cannon|T9]] [[automatic cannon|cannon]], later produced by [[Oldsmobile]], firing through the center of the propeller hub for optimum accuracy and stability. This happened because H.M. Poyer, designer for project leader Robert Woods, was impressed by the power of this weapon and pressed for its incorporation. This was unusual, because fighter design had previously been driven by the intended engine, not the weapon. Although the T9 was devastating when it worked, it had very limited ammunition, a low rate of fire, and was prone to jamming.<ref>McDowell 1980, p. 10.</ref><ref>{{cite web |last1=Jackson |first1=David D |title=The Oldsmobile Division of General Motors in World War Two |url=http://usautoindustryworldwartwo.com/General%20Motors/Olds.htm |website=The American Automobile Industry in World War Two |access-date=19 July 2022}}</ref>

A secondary benefit of the mid-engine arrangement was that it created a smooth and streamlined nose profile. Much was made of the fact that this resulted in a configuration "with as trim and clean a fuselage nose as the snout of a high-velocity bullet".<ref>Woods 1941{{page needed|date=September 2011}}</ref> Entry to the cockpit was through side doors (mounted on both sides of the cockpit) rather than a sliding canopy. Its unusual engine location and the long drive shaft caused some concern to pilots at first, but experience showed this was no more of a hazard in a crash landing than with an engine located forward of the cockpit. There were no problems with propeller shaft failure.

[[File:Bell P-39 Airacobra center fuselage detail.jpg|thumb|Bell P-39 Airacobra center fuselage detail with maintenance panels open]]

===XP-39 developments===
The XP-39 made its maiden flight on 6 April 1938.<ref name="Angelucci and Bowers p.41"/> at [[Wright-Patterson Air Force Base|Wright Field]], Ohio, achieving {{cvt|390|mph}} at {{cvt|20000|ft|-3}}, reaching this altitude in only five minutes.<ref>Johnsen 1998, p. 7.</ref> However, the XP-39 was found to be short on performance at altitude. Flight testing had found its top speed at {{cvt|20000|ft|-3}} to be lower than the {{cvt|400|mph}} of the original proposal.<ref name=Matthews85 />

As originally specified by Kelsey and Saville, the XP-39 had a turbo-supercharger to augment its high-altitude performance. Bell cooled the turbo with a scoop on the left side of the fuselage.<ref>Johnsen 1998, p. 8.</ref> Kelsey wished to shepherd the XP-39 through its early engineering teething troubles, but he was ordered to England. The XP-39 project was handed over to others, and in June 1939 the prototype was ordered by General [[Henry H. Arnold]] to be evaluated in [[NACA]] wind tunnels to find ways of increasing its speed, by reducing parasitic drag.<ref name=Pearcy>Pearcy 1993, p. 25.</ref> Tests were carried out, and Bell engineers followed the recommendations of NACA and the Army to reduce drag such that the top speed was increased 16%.<ref name=Pearcy/> NACA wrote, "it is imperative to enclose the supercharger within the airplane with an efficient duct system for cooling the rotor and discharging the cooling air and exhaust gases."<ref name=AAHS2001/> In the very tightly planned XP-39, though, there was no internal space left over for the turbo. Using a drag-buildup scheme, potential areas of drag reduction were found. NACA concluded that a top speed of {{cvt|429|mph}} could be realized with the aerodynamic improvements they had developed and an uprated V-1710 with only a single-stage, single-speed supercharger.<ref>Matthews 1996, p. 97.</ref>

At a pivotal meeting with the USAAC and NACA in August 1939, [[Lawrence Dale Bell|Larry Bell]] proposed that the production P-39 aircraft be configured without the turbocharger.<ref>Matthews 1996, p. 101.</ref> Some historians have questioned Bell's true motivation in reconfiguring the aircraft. The strongest hypothesis is that Bell's factory did not have an active production program and he was desperate for cash flow. Other historians mention that wind tunnel tests made the designers believe the turbocharger installation was so aerodynamically cluttered that it had more disadvantages than advantages.<ref>Matthews 1996, p. 102.</ref><ref>Lednicer 2000, p. 2.</ref>

The Army ordered 12 YP-39s (with only single-stage, single-speed superchargers) for service evaluation<ref name= "Donald">Donald 1997{{page needed|date=September 2011}}</ref> and one YP-39A. After these trials were complete, which resulted in detail changes including deletion of the external radiator,<ref name= "Donald"/><ref name="Fitzsimons">Fitzsimons 1977, p. 50.</ref> and on advice from [[National Advisory Committee on Aeronautics|NACA]],<ref name= "Donald"/> the prototype was modified as the ''XP-39B''; after demonstrating a performance improvement,<ref name= "Donald"/> the 13 YP-39s were completed to this standard, adding two {{cvt|0.30|in|2}} machine guns to the two existing {{cvt|0.50|in|1}} guns.<ref name= "Donald"/> Lacking armor or self-sealing fuel tanks, the prototype was {{cvt|2000|lb|-2}} lighter than the production fighters.<ref>Kinzey 1999, pp. 9, 13.</ref>

The production P-39 retained a single-stage, single-speed supercharger with a critical altitude (above which performance declined) of about {{cvt|12000|ft}}.<ref>Dean 1997, p. 191.</ref> As a result, the aircraft was simpler to produce and maintain. However, the removal of the turbo destroyed any chance that the P-39 could serve as a high-altitude front-line fighter. When deficiencies were noticed in 1940 and 1941, the lack of a turbo made it nearly impossible to improve upon the Airacobra's performance.{{refn|Quote: "With the turbo, Bell's fighter had outstanding performance in spite of the associated drag penalties NACA aerodynamicists found so objectionable. Elimination of the turbo without substituting comparable gear-driven supercharger performance relegated the airplane to an 'also-ran'..."<ref name=AAHS2001>''AAHS Journal'' 2001, pp. 295–297.</ref>"... there is no doubt that the deletion of the turbo-supercharger ruined the P-39."<ref>Dwyer, Larry. [http://www.aviation-history.com/engines/allison.htm "Allison V-1710 – USA."] ''Aviation-History.com,'' 6 August 2005. Retrieved: 25 March 2009.</ref>|group=N}} The removal of the turbocharger and its drag-inducing inlet cured the drag problem but reduced performance overall.<ref name=AAHS2001/> In later years, Kelsey expressed regret at not being present to override the decision to eliminate the turbo.<ref>Kelsey 1982{{page needed|date=September 2011}}</ref>

After completing service trials, and originally designated ''P-45'', a first order for 80 aircraft was placed 10 August 1939; the designation reverted to P-39C before deliveries began. After assessing aerial combat conditions in Europe, it was evident that without armor or self-sealing tanks, the 20 production P-39Cs were not suitable for operational use. The remaining 60 machines in the order were built as P-39Ds with armor, self-sealing tanks and enhanced armament. These P-39Ds were the first Airacobras to enter into service with the Army Air Corps units and would be the first ones to see action.<ref name= "Donald"/>

===Technical details===
[[File:Bell P-39K-L internal.png|thumb|Bell P-39K-L internal layout from ''Pilot's Flight Operating Instructions P-39K-1 and P-39L-1 (T.O. No. 01-110FG-1)'']]
The P-39 was an all-metal, low-wing, single-engine fighter with a tricycle undercarriage and an [[Allison V-1710]] liquid-cooled V-12 engine mounted in the central fuselage, directly behind the cockpit.

The Airacobra was one of the first production fighters to be conceived as a "weapons system"; in this case the aircraft (known originally as the Bell Model 4) was designed to provide a platform for the [[M4 cannon|37&nbsp;mm T9 cannon]].<ref name="Bowers 1978, p.24.">Bowers 1978, p. 24.</ref> This weapon, which was designed in 1934 by the American Armament Corporation, a division of [[Oldsmobile]], fired a {{cvt|1.3|lb|g}} projectile capable of piercing {{cvt|0.8|in}} of armor at {{cvt|500|yd}} with [[armor piercing|armor-piercing]] rounds. The {{cvt|90|in|m}}-long, {{cvt|200|lb|-1}} weapon had to be rigidly mounted and fire parallel to and close to the centerline of the new fighter. It would have been impossible to mount the weapon in the fuselage, firing through the cylinder banks of the [[V engine|Vee-configured engine]] and the propeller hub as could be done with smaller 20&nbsp;mm cannon. Weight, balance and visibility considerations meant that the cockpit could not be placed farther back in the fuselage, behind the engine and cannon.<ref name="Bowers 1978, p.24."/> The solution adopted was to mount the cannon in the forward fuselage and the engine in the center fuselage, directly behind the pilot's seat. The tractor propeller was driven with a {{convert|10|ft|m|0|adj=mid|-long}} drive shaft made in two sections, incorporating a self-aligning bearing to accommodate fuselage deflection during violent maneuvers. This shaft ran through a tunnel in the cockpit floor and was connected to a gearbox in the nose of the fuselage which, in turn, drove the three- or (later) four-bladed propeller by way of a short central shaft. The gearbox was provided with its own lubrication system, separate from the engine; in later versions of the Airacobra the gearbox was provided with some armor protection.<ref name="Bowers 1978, p.24."/> The [[Ethylene glycol|glycol]]-cooled radiator was fitted in the wing center section, immediately beneath the engine; this was flanked on either side by a single drum-shaped oil cooler. Air for the radiator and oil coolers was drawn in through intakes in both wing-root leading edges and was directed via four ducts to the radiator faces. The air was then exhausted through three controllable hinged flaps near the trailing edge of the center section. Air for the [[carburetor]] was drawn in through a raised oval intake immediately aft of the rear canopy.<ref name="Green and Swanborough 1977, pp.8–9.">Green and Swanborough 1977, pp. 8–9.</ref><ref>[http://www.zenoswarbirdvideos.com/Images/P-39/P39CoolSys.pdf "P-39 cooling system (PDF File)."] ''zenoswarbirdvideos.com.'' Retrieved: 12 May 2009.</ref>

The fuselage structure was unusual and innovative, being based on a strong central keel that incorporated the armament, cockpit, and engine. Two strong fuselage beams to port and starboard formed the basis of the structure. These angled upwards fore and aft to create mounting points for the T9 cannon and propeller reduction gearbox and for the engine and accessories respectively. A strong arched bulkhead provided the main structural attachment point for the main spar of the wing. This arch incorporated a fireproof panel and an armor plate between the engine and the cockpit. It also incorporated a turnover pylon and a pane of bullet-resistant glass behind the pilot's head. The arch also formed the basis of the cockpit housing; the pilot's seat was attached to the forward face as was the cockpit floor. Forward of the cockpit the fuselage nose was formed from large removable covers. A long nose wheel well was incorporated in the lower nose section. The engine and accessories were attached to the rear of the arch and the main structural beams; these too were covered using large removable panels. A conventional semi-monocoque rear fuselage was attached aft of the main structure.<ref name="Green and Swanborough 1977, pp.8–9."/>{{refn|Note: Photographs of the P-39's structure can be found in images from: [http://www.pacificwrecks.com/people/visitors/gillis/tsili-tsili-p39.html "Image of P-39 structure."], [http://www.pacificwrecks.com/aircraft/p-39/41-7215/side-jig.html "P-39 recovered fuselage structure."], [http://www.pacificwrecks.com/aircraft/p-39/41-7215/cockpit.html "P-39 Cockpit and rear arch."] ''pacificwrecks.com.'' Retrieved: 12 May 2009.|group=N}}

[[File:P-39Q Airacobra weapons bay.jpg|thumb|The weapons bay of the P-39]]

Because the pilot was above the extension shaft, he was placed higher in the fuselage than in most contemporary fighters, which, in turn gave the pilot a good field of view.<ref name="Bowers 1978, p.24."/> Access to the cockpit was by way of sideways opening "car doors", one on either side. Both had wind-down windows. As only the right-hand door had a handle both inside and outside this was used as the normal means of access and egress. The left-hand door could be opened only from the outside and was for emergency use, although both doors could be jettisoned. In operational use, as the roof was fixed, the cockpit design made escape difficult in an emergency.<ref>Johnson and Heffernan 1982, p. 90.</ref>

The complete armament fit consisted of the T9 cannon with a pair of [[M2 Browning machine gun|Browning M2 {{cvt|.50|in|1}}]] [[machine gun]]s mounted in the nose. This changed to two .50 caliber and two {{cvt|.30|in|2}} guns in the XP-39B (P-39C, Model 13, the first 20 delivered) and two .50s and four .30s (all four in the wings) in the P-39D (Model 15), which also introduced self-sealing tanks and shackles (and piping) for a {{cvt|500|lb}} bomb or drop tank.<ref name= "Donald"/>

Because of the unconventional layout, there was no space in the fuselage to place a fuel tank. Although drop tanks were implemented to extend its range, the standard fuel load was carried in the wings, with limitations on range.<ref>Dean 1997, pp. 191–192.</ref>

A heavy structure, and around {{cvt|256|lb}} of armor, were characteristic of this aircraft as well. The production P-39's heavier weight combined with the Allison engine with only a single-stage, single-speed supercharger, limited high-altitude performance, which was markedly inferior to contemporary European fighters and, as a result, the first USAAF fighter units in the [[European theatre of World War II|European Theater]] were equipped with the [[Supermarine Spitfire (early Merlin-powered variants)#Mk V (Types 331, 349 and 352)|Spitfire V]]. However, the P-39D's roll rate was 75°/s at {{cvt|235|mph}} – better than the [[Mitsubishi A6M Zero|A6M2]], [[Grumman F4F Wildcat|F4F]], or [[Lockheed P-38 Lightning|P-38]] up to {{cvt|265|mph}}.<ref>Dean 1997, pp. 192, 602.</ref>

Above the supercharger's peak altitude of about {{cvt|12000|ft}}, performance dropped off rapidly, limiting usefulness in traditional fighter missions in Europe as well as in the Pacific, where it was not uncommon for Japanese bombers to attack from above the P-39's ceiling (which in the tropical heat was lower than in cooler climates). The late production N and Q models, which made up 75% of Airacobras built, could maintain a top speed of {{cvt|375|mph|km/h kn}} up to {{cvt|20000|ft|-3}}.

Weight distribution could result in it entering a dangerous [[Flat spin (aviation)|flat spin]], a characteristic Soviet test pilots demonstrated to the skeptical manufacturer, which had been unable to reproduce the effect. It was determined the spin could only be induced if the aircraft were flown with no ammunition in the nose. The flight manual noted a need to ballast the front ammunition compartment to achieve a reasonable [[Center of mass|center of gravity]]. High-speed controls were light, consequently high-speed turns and pull-outs were possible. The P-39 had to be held in a dive since it tended to level out and the recommended never-exceed dive speed limit ([[Vne]]) was {{cvt|475|mph|km/h kn}}.<ref>Dean 1997, p. 200.</ref>

Soon after entering service, pilots began to report that "during flights of the P-39 in certain maneuvers, it tumbled end over end." Most of these events happened after the aircraft was stalled in a nose high attitude with considerable power applied. Bell pilots made 86 separate efforts to reproduce the reported tumbling characteristics. In no case were they able to tumble it. In his autobiography veteran test and airshow pilot [[Bob Hoover|R.A. "Bob" Hoover]] provides an account of tumbling a P-39. He goes on to say that in hindsight, he was actually performing a ''[[Lomcovak]]'', a now-common airshow maneuver, which he was also able to do in a [[Curtiss P-40]].<ref>Hoover and Shaw 1996, pp. 25–26.</ref>{{Refn| In any of several variations, the Lomcovak involves autorotating the aircraft end over end at the apex of a climbing outside snap roll. Most Lomcovaks are entered from a near vertical attitude with power applied, which matches the description of how P-39 tumbles were entered.<ref>Williams 1975{{page needed|date=September 2011}}</ref>|group=N}}  A study of its spinning characteristics was conducted in the [[NASA Langley Research Center]] {{convert|20|ft|m|adj=on|0}} Free-Spinning Tunnel during the 1970s. A study of old reports showed that during earlier tests the aircraft never tumbled. However, it was noted that all testing had been done with a simulated full ammunition load, which moved the center of gravity forward. After finding the original spin test model of the P-39 in storage, the new study first duplicated the earlier tests, with consistent results. Then, the model was re-ballasted to simulate a condition with no ammunition load, which moved the aircraft's center of gravity aft. Under these conditions, the model was found to tumble.<ref>Lednicer 2000, p. 7.</ref>

The rear-mounted engine was less likely to be hit when attacking ground targets, but was vulnerable to attacks from above and behind. At its upper altitude limits, the Airacobra was out-performed by many enemy aircraft.<ref>Dean 1997, pp. 206–207.</ref>
[[File:Bell P-39 Airacobra in flight firing all weapons at night.jpg|thumb|Bell P-39 Airacobra firing all weapons at night]]

=== Service and versions ===
In September 1940, Britain ordered 386 P-39Ds (Model 14), with a 20&nbsp;mm [[Hispano-Suiza HS.404]] and six [[.303 British|{{cvt|.303|in|1}}]] instead of a 37&nbsp;mm cannon and six .30 caliber guns. The RAF eventually ordered 675 P-39s. However, after the first Airacobras arrived at [[No. 601 Squadron RAF|601 Squadron]] [[Royal Air Force|RAF]] in September 1941, they were found to have an inadequate rate of climb and performance at altitude for Western European conditions. Only 80 were operated, all by 601 Squadron. Britain transferred about 200 P-39s to the Soviet Union.

Another 200 examples intended for the RAF were taken up by the [[United States Army Air Forces|USAAF]] after the [[attack on Pearl Harbor]] as the ''P-400'', and were sent to the [[Fifth Air Force]] in Australia, for service in the [[South West Pacific theatre of World War II|South West Pacific Theatre]].<ref>Dean 1997, p. 194.</ref>

By the date of the Pearl Harbor attack, nearly 600 P-39s had been built. When P-39 production ended in August 1944, Bell had built 9,558<ref name= "Donald"/><ref name="Fitzsimons"/> Airacobras, of which 4,773 (mostly −39Ns and −39Qs<ref name= "Donald"/>) were sent to the Soviet Union through the [[Lend-lease|Lend-Lease program]]. There were numerous minor variations in engine, propeller, and armament, but no major structural changes in production types, excepting a few two-seat TP-39F and RP-39Q trainers.<ref>Donald 1997, p. 107.</ref>{{refn|Trainers were a rarity for fighter types outside the Soviet Union in the 1940s.|group=N}} In addition, seven went to the [[US Navy]] as radio-controlled [[Remotely Piloted Vehicle|drones]].

Trials of a [[laminar flow]] wing (in the XP-39E) and [[Continental Motors Company|Continental]] IV-1430 engine (the P-76) were unsuccessful.<ref name= "Donald"/> The mid-engine, gun-through-hub concept was developed further in the [[Bell P-63 Kingcobra]].

A naval version with tailwheel landing gear, the [[Bell XFL Airabonita|XFL-1 Airabonita]], was ordered as a competitor to the [[Vought F4U Corsair]] and [[Grumman XF5F Skyrocket]]. It first flew 13 May 1940,<ref name= "Donald"/> but after a troublesome and protracted development and testing period, it was rejected.
[[File:Bell P-39Q.jpg|thumb|Bell P-39Q]]

==Operational history==
The Airacobra saw combat throughout the world, particularly in the Southwest Pacific, Mediterranean and Soviet theaters. Because its engine was equipped with only a single-stage, single-speed supercharger, the P-39 performed poorly above {{convert|17000|ft|m|-2}} altitude. In both western Europe and the Pacific, the Airacobra found itself outclassed as an interceptor and the type was gradually relegated to other duties.<ref name=" Angelucci and Matricardi p. 25."/> It often was used at lower altitudes for such missions as ground strafing.

===United Kingdom===
In 1940, the [[British Direct Purchase Commission]] in the US was looking for combat aircraft; they ordered 675 of the export version Bell Model 14 as the ''Caribou'' on the strength of the company's representations on 13 April 1940. The British armament was two nose-mounted .50 caliber machine guns and four .303 caliber [[M1919 Browning machine gun|Browning machine guns]] in the wings. The 37&nbsp;mm gun was replaced by a 20&nbsp;mm [[Hispano-Suiza HS.404|Hispano-Suiza cannon]].

British expectations had been set by performance figures established by the unarmed and unarmored XP-39 prototype. The British production contract stated that a maximum speed of {{cvt|394|mph}} +/- 4% was required at rated altitude.<ref name=Matthews120>Matthews 1996, p. 120.</ref> In acceptance testing, actual production aircraft were found to be capable of only {{cvt|371|mph}} at {{cvt|14090|ft}}. To enable the aircraft to make the guaranteed speed, a variety of drag-reduction modifications were developed by Bell. The areas of the elevator and rudder were reduced by 14.2% and 25.2% respectively. Modified fillets were installed in the tail area. The canopy glass was faired to its frame with putty. The gun access doors on the wing had been seen to bulge in flight, so they were replaced with thicker aluminum sheet. Similarly, the landing gear doors deflected open by as much as two inches at maximum speed, so a stronger linkage was installed to hold them flush. The cooling air exit from the oil and coolant radiators was reduced in area to match the exit velocity to the local flow. New engine exhaust stacks, deflected to match the local flow and with nozzles to increase thrust augmentation, were installed. The machine gun ports were faired over, the antenna mast was removed, a single-piece engine cowling was installed and an exhaust stack fairing was added.

[[File:Airacobra 601 Sqn.JPG|thumb|left|601 Squadron Airacobra I. The long-barrelled [[Hispano-Suiza HS.404|20 mm Hispano-Suiza cannon]] Hispano is clearly shown, as are the .303 wing guns.]]

The airframe was painted with 20 coats of primer, with extensive sanding between coats. Standard camouflage was applied and sanded to remove the edges between the colors. Additionally, about {{cvt|200|lb}} of weight was removed, making it lighter than normal ({{cvt|7466|lb}} gross).<ref>Matthews 1996, pp. 119–120.</ref> After these modifications, the second production aircraft ([[United Kingdom military aircraft serials|serial]] ''AH 571'') reached a speed of {{cvt|391|mph}} at {{cvt|14,400|ft}} in flight test. As this speed was within 1% of the guarantee, the aircraft was declared to have satisfied contractual obligations.<ref name=Matthews120 /> Despite the success of these modifications, none were applied to other production P-39s. Later testing of a standard production P-400 by the British [[Aeroplane and Armament Experimental Establishment]] (A&AEE) revealed a top speed of only {{cvt|359|mph}}.<ref>"The Calamitous ‘Cobra'." ''Air Enthusiast,'' Vol. 1, No. 3, August 1971.</ref>

The British export models were renamed ''Airacobra'' in 1941. A further 150 were specified for delivery under [[Lend-Lease]] in 1941 but these were not supplied. The [[Royal Air Force]] (RAF) took delivery in mid-1941 and found that performance of the non-turbo-supercharged production aircraft differed markedly from what they were expecting.<ref>Mason 1969, pp. 5–6.</ref> In some areas, the Airacobra was inferior to existing aircraft such as the [[Hawker Hurricane]] and [[Supermarine Spitfire]] and its performance at altitude suffered drastically. Tests by the [[Royal Aircraft Establishment]] at [[RAF Boscombe Down|Boscombe Down]] showed the Airacobra reached {{cvt|355|mph}} at {{cvt|13000|ft}}.<ref>Johnson and Heffernan 1982, p. 93.</ref> The cockpit layout was criticized, and it was noted that the pilot would have difficulty in bailing out in an emergency because the cockpit roof could not be jettisoned. The lack of a clear vision panel on the windscreen assembly meant that in the event of heavy rain the pilot's forward view would be obliterated; the pilot's notes advised that in this case the door windows would have to be lowered and the speed reduced to {{cvt|150|mph}}<ref>Johnson and Heffernan 1982, pp. 91–92.</ref> On the other hand, it was considered effective for low level fighter and ground attack work. Problems with gun- and exhaust-flash suppression and the compass could be fixed.

[[No. 601 Squadron RAF]] was the only British unit to use the Airacobra operationally, receiving their first two examples on 6 August 1941. On 9 October, four Airacobras attacked enemy barges near Dunkirk, in the type's only operational action with the RAF. The squadron continued to train with the Airacobra during the winter, but a combination of poor serviceability and deep distrust of this unfamiliar fighter resulted in the RAF rejecting the type after one combat mission.<ref name="Gunston p. 22"/> In March 1942, the unit re-equipped with Spitfires.

The Airacobras already in the UK, along with the remainder of the first batch being built in the US, were sent to the Soviet Air force, the sole exception being ''[[AH574]]'', which was passed to the [[Royal Navy]] and used for experimental work, including the first carrier landing by a tricycle undercarriage aircraft, on 4 April 1945 on {{HMS|Pretoria Castle|F61|6}},<ref>Brown 2006, p. 93.</ref> until it was scrapped on the recommendation of a visiting Bell test pilot in March 1946.<ref>Brown 2006, p. 145.</ref>

===US Army Air Forces===

====Pacific====
[[File:72nd Tactical Recon Group P-39.jpg|thumb|72nd Tactical Recon Group P-39, c. 1942]]
The United States requisitioned 200 of the aircraft being manufactured for the UK, adopting them as P-400s. After the [[attack on Pearl Harbor]], the P-400 was deployed to training units, but some saw combat in the Southwest Pacific including with the [[Cactus Air Force]] in the [[Battle of Guadalcanal]].<ref>Baugher, Joe. [http://www.joebaugher.com/usaf_fighters/p39_5.html "Airacobra I for RAF, P-400."] {{Webarchive|url=https://web.archive.org/web/20101104092559/http://joebaugher.com/usaf_fighters/p39_5.html |date=4 November 2010 }} ''Bell P-39 Airacobra'', 4 August 2010. Retrieved: 16 September 2010.</ref> Though outclassed by Japanese fighter aircraft, it performed well in strafing and bombing runs, often proving deadly in ground attacks on Japanese forces trying to retake [[Battle for Henderson Field|Henderson Field]]. Guns salvaged from P-39s were sometimes fitted to Navy [[PT boat]]s to increase firepower. Pacific pilots often complained about problems of performance and unreliable armament, but by the end of 1942, the P-39 units of the Fifth Air Force had claimed about 80 Japanese aircraft, with a similar number of P-39s lost. Fifth and Thirteenth air force P-39s did not score more aerial victories in the Solomons due to the aircraft's limited range and poor high altitude performance.

Airacobras first fought Japanese [[Mitsubishi A6M Zero|A6M Zeros]] on 30 April 1942 in a low level action near Lae, New Guinea. From May to August 1942 combat between Airacobras and Zeros took place on a regular basis over New Guinea. Compilation of combat reports indicates the Zero was either equal to or close to the P-39 in speed at the altitudes of the various low level encounters.

From September to November 1942, pilots of the [[57th Fighter Squadron]] flew P-39s and P-38s from an airfield built on land bulldozed into [[Kuluk Bay]] on the barren island of [[Adak Island|Adak]] in Alaska's [[Aleutian Islands]]. They attacked the Japanese forces that had invaded Attu and Kiska islands in the Aleutians in June 1942. The factor that claimed the most lives was not the Japanese but the weather. The low clouds, heavy mist and fog, driving rain, snow, and high winds made flying dangerous and lives miserable. The 57th remained in Alaska until November 1942, then returned to the United States.

[[File:P-400 in Pacific.jpg|thumb|left|USAAF P-400 of 80th Fighter Squadron "Headhunters", 8th Fighter Group]]

While Lieutenant [[William F. Fiedler|Bill Fiedler]] was the only American pilot to become an ace in a P-39, many later US aces scored one or two of their victories in the type. The Airacobra's low-altitude performance was good and its firepower was impressive; regardless, it soon became a joke in the Pacific Theatre that a P-400 was a P-40 with a Zero on its tail.<!--is that remark in Pejčoch?--><ref>Pejčoch 2008, p. 86.</ref>

====Mediterranean====
In North Africa, the [[99th Fighter Squadron]] (also known as the [[Tuskegee Airmen]]) transitioned quickly from the P-40 and were assigned P-39s in February 1944, but only flew the type for a few weeks. The 99th carried out their duties including supporting [[Operation Shingle]] over [[Anzio]] as well as missions over the [[Gulf of Naples]] in the Airacobra but achieved few aerial victories.<ref>[http://www.tuskegeeairmen.org/uploads/stats.pdf "The combat record of the Tuskegee Airmen speaks for itself."] {{webarchive |url=https://web.archive.org/web/20101130173210/http://www.tuskegeeairmen.org/uploads/stats.pdf |date=30 November 2010 }} ''tuskegeeairmen.org''. Retrieved: 16 October 2009.</ref>

The major MTO P-39 operators included the [[81st Fighter Group|81st]] and [[350th Fighter Group]]s, both flying the maritime patrol mission from North Africa and on through Italy. The 81st transferred to the [[China Burma India Theater]] by March 1944 and the 350th began transition to the P-47D in August 1944, remaining in Italy with the 12th Air Force.

===Soviet Union===
[[File:P-39 Airacobra 2006-06-15.jpg|thumb|Soviet P-39Q formerly ''44-2664'' on display at the Aviation Museum of Central Finland]]
Nearly half of all P-39s were sent to the Soviet Union: 4,719, accounting for more than one-third of all US and UK-supplied fighter aircraft in the VVS.<ref>Hardesty 1991, p. 253.</ref> The [[Soviet Air Forces]] received the considerably improved N and Q models via the [[Northwest Staging Route|Alaska-Siberia ferry route]]. The tactical environment of the [[Eastern Front (World War II)|Eastern Front]] suited the P-39's strengths—sturdy construction, reliable radio gear, and good firepower—and did not demand the high-speed, high-altitude performance of  RAF and USAAF operations.  

The first Soviet Cobras had a 20&nbsp;mm Hispano-Suiza cannon and two heavy Browning machine guns, synchronized and mounted in the nose. Later Cobras arrived with the M4 37&nbsp;mm cannon and four machine guns, two synchronized and two wing-mounted. "We immediately removed the wing machine guns, leaving one cannon and two machine guns," Golodnikov recalled later.<ref name="Drabkin p. 133." /> That modification improved roll rate by reducing [[rotational inertia]]. Soviet airmen appreciated the M4 cannon with its powerful rounds and the reliable action but complained about the low rate of fire (three rounds per second) and inadequate ammunition storage (only 30 rounds).<ref name="Drabkin p. 133." /> The United States did not supply M80 armor-piercing rounds for the [[autocannon]]s of Soviet P-39s; instead, the Soviets received 1,232,991 [[M4 cannon#Ammunition|M54 high-explosive]] rounds, which they used primarily for air-to-air combat and against soft ground targets. The VVS did not use the P-39 for [[Anti-tank warfare|tank-busting]].<ref>Loza and Gebhardt 2002, p. 359.</ref>

The Soviets used the Airacobra primarily for air-to-air combat.<ref>Gebhardt, Major James F., USAF (Retired). [http://www.marchfield.org/p39q.htm "Some Additional P-39 History."] {{webarchive|url=https://web.archive.org/web/20091214233631/http://www.marchfield.org/p39q.htm|date=14 December 2009}} ''March Field Air Museum''. Retrieved: 29 October 2009.</ref> They developed successful group aerial fighting tactics, and scored an outsized number of aerial victories over a variety of German aircraft, including Bf 109s, [[Focke-Wulf Fw 190]]s, Ju 87s, and [[Junkers Ju 88|Ju 88]]s. Soviet P-39s had no trouble dispatching [[Junkers Ju 87]] ''Stuka''s or German twin-engine bombers and matched, and in some areas surpassed, early and mid-war [[Messerschmitt Bf 109]]s. The usual nickname for the Airacobra in the ''VVS'' was ''Kobrushka'' ("little cobra") or ''Kobrastochka'', a blend of Kobra and ''Lastochka'' (swallow), "dear little cobra".<ref>Mitchell 1992, p. 34.</ref>

A common Western misconception is that the Bell fighters were used as ground attack aircraft. This is because the Soviet term for the mission of the P-39, ''prikrytiye sukhoputnykh voysk'' (coverage of ground forces) has been mistaken as meaning [[close air support]]. In Soviet usage, it has a broader meaning including protection of the airspace above army operations. Strafing was mostly handled by thousands of heavily armored [[Ilyushin Il-2]] aircraft; while Soviet-operated P-39s did make strafing attacks, it was "never a primary mission or strong suit for this aircraft".<ref>Colonel Dmitriy Loza, Red Army. Loza and Gebhardt 2002, pp. 15–16.</ref> 

{{quote box|align=left|width=30%|quote="I liked the Cobra, especially the Q-5 version. It was the lightest version of all Cobras and was the best fighter I ever flew. The cockpit was very comfortable, and visibility was outstanding. The instrument panel was very ergonomic, with the entire complement of instruments right up to an artificial horizon and radio compass. It even had a relief tube in the shape of a funnel. The armored glass was very strong, extremely thick. The armor on the back was also thick. The oxygen equipment was reliable, although the mask was quite small, only covering the nose and mouth. We wore that mask only at high altitude. The HF radio set was powerful, reliable and clear."|source=<small>Soviet pilot Nikolai G. Golodnikov, recalling his experiences of the P-39<ref name= "Drabkin p. 133.">Drabkin 2007, p. 133.</ref></small>}}

During the battle of [[Kuban]] River, VVS relied on P-39s much more than Spitfires and P-40s. [[Aleksandr Pokryshkin]], from 16.''Gv.IAP'' ([[16th Guards Fighter Aviation Division|16th Guards Fighter Aviation Regiment]]), claimed 20 victories in that campaign in a P-39.<ref name="Morgan p. 20.">Morgan  1999, p. 20.</ref>

[[File:Postwar P-39.jpg|thumb|Former USAAF flown post-war by the [[Commemorative Air Force]] in Soviet markings, c. 1990s]]

The last plane shot down by the Luftwaffe was a Soviet P-39, on 8 May by ''Oblt.'' Fritz Stehle of 2./JG 7 flying a [[Messerschmitt Me 262|Me 262]] over the [[Ore Mountains]].<ref>{{Cite book|title= Bagration to Berlin: The Final Air Battles in the East: 1944–1945 | last = Bergstrom| first = Christer | publisher = Ian Allan|year=2008| isbn = 978-1-903223-91-8 |location=Great Britain|pages=123–124}}</ref>
The last Soviet air victory was in a P-39 on 9 May when ''Kapitan'' Vasily Pshenichikov downed a [[Focke-Wulf Fw 189]] over [[Prague]].<ref>{{Cite book|title= Bagration to Berlin: The Final Air Battles in the East: 1944–1945 | last = Bergstrom| first = Christer | publisher = Ian Allan|year=2008| isbn = 978-1-903223-91-8 |location=Great Britain|page=124}}</ref>
Half of the 10 highest-scoring Soviet aces logged the majority of their kills in P-39s. [[Grigoriy Rechkalov]] scored 44 victories in Airacobras. Pokryshkin scored 47 of his 59 victories in P-39s, making him the highest-scoring P-39 fighter pilot of any nation, and the highest-scoring Allied fighter pilot using an American fighter.<ref>{{cite book |url=https://books.google.com/books?id=614bVlv32nwC&pg=PA114 |page=114 |last1=Saltzman |first1=B. Chance |last2=Searle |first2=Thomas R. |title=Introduction to the United States Air Force |publisher=Airpower Research Institute, Air University Press |date=2001 |isbn=978-1-4289-2621-9}}</ref> This does not include his 6 shared victories, at least some of which were achieved with the P-39.


Soviet Airacobra losses totalled 1,030 aircraft (49 in 1942, 305 in 1943, 486 in 1944 and 190 in 1945).<ref name="Bergström p.132">Bergström 2008, p. 132.</ref>

Airacobras served with the Soviet Air Forces as late as 1949, when two regiments were operating as part of the [[16th Guards Fighter Aviation Division]] in the [[Belomorsky Military District]].<ref>Holm, Michael. [http://www.ww2.dk/new/air%20force/division/iad/16gviad.htm "P=39."] {{webarchive |url=https://web.archive.org/web/20120401124839/http://www.ww2.dk/new/air%20force/division/iad/16gviad.htm |date=1 April 2012 }} ''ww2.dk.'' Retrieved: 26 September 2011.</ref>

===Australia===
[[File:Airacobra I RAAF in 1942.jpg|thumb|A RAAF P-39 Airacobra on loan from the US Fifth Airforce and came to Australia in April 1942 to train RAAF pilots. It was damaged on 10 February 1943 and written off on 1 April 1944. There is a US star on the wing.]]
A total of 23 re-conditioned Airacobras, on loan from the US [[Fifth Air Force]] (5 AF), were used by the [[Royal Australian Air Force]] (RAAF) as a stop-gap interceptor in rear areas. The aircraft were assigned the RAAF serial prefix A53.<ref name="crick">Crick, Darren. [http://www.adf-serials.com.au/2a53.shtml "RAAF A53 Bell P-39D/F Airacobra"] {{Webarchive|url=https://web.archive.org/web/20130510052907/http://www.adf-serials.com.au/2a53.shtml |date=2013-05-10 }} ''adf-serials.com'', 2006. Retrieved: 28 August 2013.</ref>

In the early months of the Pacific War, the RAAF was able to obtain only enough [[Curtiss P-40 Warhawk|Curtiss Kittyhawk]]s to equip three squadrons, destined for front-line duties in [[New Guinea]].<ref name="Birkett">Birkett, Gordon R. [http://www.adf-serials.com/research/Airacobra.pdf "RAAF Bell Airacobras Part 1."] ''adf-serials.com'', 2005. Retrieved: 20 June 2007.</ref> and – in the face of increasing [[Air raids on Australia, 1942–43|Japanese air raids on towns in northern Australia]] – was forced to rely on the P-40, P-39, and P-400 units of 5 AF for the defence of areas such as [[Darwin, Northern Territory|Darwin]]. During mid-1942, USAAF P-39 units in Australia and New Guinea began to receive brand new P-39Ds.<ref name="Birkett"/> Consequently, P-39s that had been repaired in Australian workshops were loaned by 5 AF to the RAAF. In July, seven P-39Fs arrived at [[No. 24 Squadron RAAF|24 Squadron]], in [[Bankstown Airport|RAAF Bankstown]] in Sydney.<ref name="crick"/><ref name="Birkett"/> In August, seven P-39Ds were received by [[No. 23 Squadron RAAF]] at [[Lowood Airfield]], near [[Brisbane]].<ref name="crick"/><ref name="Birkett"/> Both squadrons also operated other types, such as the [[CAC Wirraway]] armed [[training aircraft|trainer]]. Neither squadron received a full complement of Airacobras or saw combat with them. From early 1943, the air defence role was filled by a wing of Spitfires.

Both 23 and 24 Squadron converted to the [[Vultee Vengeance]] [[dive bomber]] in mid-1943, their P-39s transferred to two newly formed fighter squadrons: [[No. 82 Squadron RAAF|No. 82]] (augmenting P-40s, still in short supply) at Bankstown and [[No. 83 Squadron RAAF|No. 83]] (as it awaited the Australian-designed [[CAC Boomerang]]) in [[Strathpine, Queensland|Strathpine]], near Brisbane.<ref name="crick"/> After serving with these squadrons for a few months, the remaining Airacobras were returned to the USAAF and the RAAF ceased to operate the type.<ref name="crick"/>

===France===
In 1940, France ordered P-39s from Bell, but because of the [[Armistice with France (Second Compiègne)|armistice with Germany]] they were not delivered. After [[Operation Torch]], French forces in North Africa sided with the Allies, and were re-equipped with Allied equipment including P-39Ns. From mid-1943 on, three fighter squadrons, the [[Groupe de Chasse 3/6|GC 3/6 ''Roussillon'']], [[Groupe de Chasse I/4|GC 1/4 ''Navarre'']] and [[Groupe de Chasse I/5|GC 1/5 ''Champagne'']], flew these P-39s in combat over the Mediterranean, Italy and Southern France. A batch of P-39Qs was delivered later, but Airacobras, which were never popular with French pilots, had been replaced by [[Republic P-47 Thunderbolt|P-47]]s in front line units by late 1944.

===Italy===
[[File:Italian P-39N 1944.jpg|thumb|Bell P-39N-1 supplied by the US Army Air Force to the Italian Regia Aeronautica's (Italian Co-Belligerent Air Force) 4th Stormo in mid-1944]]
In June 1944, the [[Italian Co-Belligerent Air Force]] (ICAF) received 170 P-39s, most of them -Qs, and a few -Ns (15th USAAF surplus aircraft stored in Napoli-Capodichino airfield) and also at least one -L and five -Ms. The P-39 N (without the underwing fairings for .50 caliber machine guns) had engines with about 200 hours; a little newer than the P-39Q engines with 30–150 hours. A total of 149 P-39s would be used: the P-39N for training, while newer Qs were used in the front line.

In June–July 1944, ''Gruppi'' 12°, 9° and 10° of 4° ''Stormo'', moved to Campo Vesuvio airstrip to re-equip with the P-39s. The site was not suitable and, in three months of training, 11 accidents occurred, due to engine failures and poor maintenance of the base. Three pilots died and two were seriously injured. One of the victims, on 25 August 1944, was the "ace of aces", ''Sergente Maggiore'' [[Teresio Vittorio Martinoli]].<ref>"Dimensione Cielo aerei Italiani nella Seconda Guerra Mondiale." ''Caccia Assalto3''. Roma: Edizioni Bizzarri, 1972, pp. 75–76.</ref>

The three groups of 4° ''Stormo'' were first sent to Leverano (Lecce) airstrip, then in mid-October, to Galatina airfield. At the end of the training, eight more accidents occurred. Almost 70 aircraft were operational, and on 18 September 1944, 12° Group's P-39s flew their first mission over Albania. Concentrating on ground attack, the Italian P-39s proved to be suitable in this role, losing 10 aircraft between 4 November and 3 December 1944,<ref name="Dimensione Cielo 1972, p. 77">Dimensione Cielo 1972, p. 77.</ref> to German flak. 
In February–March 1945, 10° and 9° ''Gruppi'' moved North of Galatina, in [[Canne, Apulia|Canne]] airbase, near [[Campobasso]], while the Allies allowed Italian pilots to use the airstrip of [[Lissa (island)|Lissa]] island, in the [[Adriatic]] sea, as an intermediate scale during the long sorties on the [[Balkans]]. The 4° ''Stormo'' pilots flew many effective ground attack missions on northern [[Yugoslavia]], losing only one more P-39, for engine failure in [[Sarajevo]] area, on 2 April 1945.<ref name="Dimensione Cielo 1972, p. 78">Dimensione Cielo 1972, p. 78.</ref>  The Italian P-39 flew over 3,000 hours of combat.<ref name="Gueli">Gueli 2004{{page needed|date=September 2011}}</ref>

By the end of the war, 89 P-39s were still at the Canne airport and 13 at the ''Scuola Addestramento Bombardamento e Caccia'' ("Training School for Bombers and Fighters") at Frosinone airfield. In 10 months of operational service, the 4° ''Stormo ''had been awarded three ''Medaglia d'Oro al Valore Militare "alla memoria"''.<ref>"Dimensione Cielo aerei Italiani nella Seconda Guerra Mondiale." ''Caccia Assalto3''. Roma: Edizioni Bizzarri, 1972, p. 78.</ref> After the war the P-39s were taken over by the [[Aeronautica Militare Italiana]] (the new Italian air force) and used for several years as training aircraft. In Galatina fighter training unit (''Scuola Caccia''), war veteran [[Lieutenant colonel|''Tenente colonnello'']] Francis Leoncini was killed during a flying accident, on 10 May 1950.<ref name="Dimensione Cielo 1972, p. 78"/>

===Portugal===
Between December 1942 and February 1943, the ''Aeronáutica Militar'' (Army Military Aviation) obtained aircraft operated by the 81st and the 350th Fighter Groups originally dispatched to North Africa as part of [[Operation Torch]]. Due to several problems en route, some of the aircraft were forced to land in Portugal and Spain. Of the 19 fighter aircraft that landed in Portugal, all were interned and entered service that year with the [[Portuguese Army]] Military Aviation. They formed the Squadron OK, based at [[Military and Technical Training Center of the Air Force|Ota Air Base]].<ref>[https://web.archive.org/web/20000415004709/http://www.geocities.com/CapeCanaveral/Hangar/9376/airacobra.htm "The P-400 / P-39L Airacobra."] ''Portuguese Airacobra service history''. Retrieved: 16 October 2009.</ref>

Though unnecessary, the Portuguese Government paid the United States US$20,000 for each of these interned aircraft as well as for one interned [[Lockheed P-38 Lightning]].<ref name="Public Record">Public Record Office entry of 18 March 1943, quoted by "Wreckovery" in ''Aviation News'', 10–23 August 1984.</ref> The US accepted the payment, and gave as a gift four additional crates of aircraft, two of which were not badly damaged, without supplying spares, flight manuals or service manuals.<ref name="Public Record"/> Without proper training, incorporation of the aircraft into service was plagued with problems, and the last six Portuguese Airacobras that remained in 1950 were sold for scrap.

==Post-war use==
A very small number of late-production P-39Qs survived long enough in the USAAF inventory to be acquired by the United States Air Force upon its separation from the Army. These aircraft served in training and testing roles for approximately a year. They were redesignated as ZF-39Qs ("ZF" for "Obsolete Fighter") in June 1948 as part of the new aircraft designation scheme throughout the USAF.

In 1945, Italy purchased the 46 surviving P-39s at 1% of their cost but in mid-1946 many accidents occurred, including fatal ones. By 1947, 4° ''Stormo'' re-equipped with [[P-38]]s, with P-39s sent to training units until the type's retirement in 1951. Only a T9 cannon survives today at Vigna di Valle Museum.<ref name="Gueli"/>

==Racing==
[[File:P-39 Airacobra racer.jpg|thumb|left|Mira Slovak's P-39Q "Mr. Mennen"]]
The Airacobra was raced at the [[National Air Races]] in the United States after World War II. Famous versions used for racing included the twin aircraft known as "Cobra I" and "Cobra II," owned jointly by Bell Aircraft test pilots [[Tex Johnston]] and [[Jack Woolams]]. These aircraft were powered by an extensively modified 2000-horsepower engine, and a [[P-63]] four-blade propeller. "Cobra I" with its pilot, Jack Woolams, was lost in 1946 during a test flight over Lake Ontario. The "Cobra II" flown by test pilot "Tex" Johnston, beat racing-modified P-51s, as well as other P-39 racers (which were the favorites), to win the 1946 [[Thompson Trophy]] race.<ref>{{cite book |last1=Johnston |first1=A.M. "Tex" |title=Tex Johnston, Jet-Age Test Pilot |date=1992 |publisher=Bantam |location=New York |isbn=9780553295870 |pages=92–108}}</ref>

''Cobra II'' competed again in the 1947 Thompson Trophy, finishing 3rd. In the 1948 Thompson trophy, it was unable to finish due to engine difficulties. ''Cobra II'' did not race again and was destroyed on 10 August 1968 during a test flight prior to an attempt at the world piston-engine air speed record, when owner-pilot Mike Carroll lost control and crashed. Carroll died and the highly modified P-39 was destroyed.

[[Mira Slovak]]'s P-39Q "Mr. Mennen" (Race #21) was a fast unlimited racer, but a late arrival in 1972 kept the {{cvt|2000|hp}} racer out of the Reno races, and it was never entered again. Its color scheme was all white with "Mennen" green and bronze trim. It is now owned and displayed by the [[Kalamazoo Air Zoo]], in the color scheme of P-400 "Whistlin' Britches."

==Variants==
{{morerefs|section|date=November 2021}}
;XP-39
:Bell Model 11,<ref name="bellp224">Pelletier 1992, p. 224</ref> one prototype ''38–326'' first flown 6 April 1938<ref name="bellp278">Pelletier 1992, pp. 27–28</ref> or 1939.<ref name="WoF10p126">Dorr 1998, p. 126</ref> Powered by a {{cvt|1150|hp}} Allison V-1710-17 (E2) engine and was fitted with a General Electric B-5 turbosupercharger, creating a two stage supercharging system similar to the P-38 (engine-mounted mechanical supercharger, remote exhaust-driven turbo-supercharger as a second stage for high-altitude). Aircraft remained unarmed. Later converted to XP-39B.<ref name="bellp278"/><ref name="WoF10p126"/>

;XP-39B
:One conversion first flown 25 November 1939. Streamlined XP-39 based on [[NACA]] [[wind tunnel]] testing resulting in revised canopy and wheel door shape, oil cooler/ engine coolant radiator intakes moved from right fuselage to wing roots, fuselage increased length by {{cvt|13|in}} and decreased wingspan (by {{cvt|22|in}}. The turbosupercharger was removed, and the single-stage, single speed, supercharged {{cvt|1090|hp}} Allison V-1710-37 (E5) engine remained. The carburetor air intake was moved behind the canopy.<ref name="bellp28,39">Pelletier 1992, pp. 28, 39</ref><ref name="WoF10p1267">Dorr 1998, pp. 126–127</ref>
[[File:P-39 1.jpg|thumb|P-39C-BE assigned to the 40th PS / 31st PG at Selfridge Field]]

;YP-39
:Bell Model 12, service test version, {{cvt|1090|hp}} V-1710-37 (E5) engine. Armed with an M4 37&nbsp;mm cannon with 15 rounds, 2 × .50 caliber machine guns with 200&nbsp;rpg, and 2 × .30 caliber machine guns with 500&nbsp;rpg in the nose. Wider vertical tail than XP-39B. 13 completed with the first flying on 13 September 1940.<ref name="bellp289">Pelletier 1992, pp. 28–29</ref><ref name="WoF10p127">Dorr 1998, p. 127</ref>

;YP-39A
:One intended to have a V-1710-31 engine, but was delivered as a regular YP-39.<ref name="WoF10p127"/>

;P-39C
:Bell Model 13, initial US Army designation P-45 Airacobra. First flown in January 1941, it was the first production version, identical to YP-39 except for {{cvt|1150|hp}} V-1710-35 engine. Armed with 1 × 37&nbsp;mm cannon, 2 × .50 caliber and 2 × .30 caliber machine guns in the nose. Aircraft lacked armor and self-sealing fuel tanks. Twenty were produced out of an order of 80, with the remainder completed as P-39Ds.<ref name="bellp29">Pelletier 1992, p. 29</ref>

;P-39D
:Bell Model 15, production variant based on the P-39C with additional armor and self-sealing fuel tanks.<ref name="bellp29"/> Armament increased to 1 × 37&nbsp;mm cannon with 30 rounds, 2 × .50 caliber and 4 × wing mounted .30 caliber machine guns; 429 produced.<ref name="bellp29"/><ref name="WoF10p129">Dorr 1998, p. 129</ref>

;;P-39D-1
:Bell Model 14A, production variant fitted with a 20&nbsp;mm M1 cannon instead of 37 mm cannon. Specifically ordered for delivery under Lend-Lease.<ref name="bellp29"/> 336 produced.<ref name="WoF10p129"/>

;;P-39D-2
:Bell Model 14A-1, production variant again intended for lend lease and fitted with 20 mm cannon, but with {{cvt|1325|hp}} V-1710-63 (E6) engine. 158 produced.<ref name="bellp29"/><ref name="WoF10p129"/>

;;P-39D-3
:26 conversions from P-39D-1 to photo reconnaissance configuration; K-24 and K-25 camera in rear fuselage, extra armor for oil coolers.<ref name="bellp29"/><ref name="WoF10p129"/>

;;P-39D-4
:11 conversions from P-39D-2 to photo reconnaissance configuration. Same modifications as D-3 aircraft.<ref name="bellp29"/><ref name="WoF10p129"/>

;XP-39E
:Bell Model 23. three P-39Ds modified for ground and flight testing first flown 21 February 1942.<ref name="Bowers 1979, p.25."/> Intended for {{cvt|2100|hp}} [[Continental XI-1430|Continental I-1430]]-1 engine but only flown with 1325&nbsp;hp Allison V-1710-47 engine. Used to test various wing and vertical tails. Fuselage lengthened by {{cvt|21|in}} and used in the development of the P-63. The production variant, with the Continental engines was to be designated [[Bell XP-76|P-76]]; there was no Bell XP-76 as such.<ref name="Bowers 1979, p.25.">Bowers 1979, p. 25.</ref>

;P-39F
:Bell Model 15B, production variant with three-bladed Aeroproducts [[constant speed propeller]]. 229 built.<ref name="bellp31">Pelletier 1992, p. 31</ref><ref name="WoF10p130">Dorr 1998, p. 130</ref>

;;P-39F-2
:27 conversions from P-39F for ground attack and tactical reconnaissance.<ref name="bellp31"/><ref name="WoF10p130"/>

;P-39G
:Bell Model 26, 1800 ordered, intended to be a P-39D-2 with a different propeller. Later cancelled, with aircraft delivered as P-39K, L, M and N.<ref name="WoF10p130"/>

;P-39J
:Bell Model 15B, P-39F with {{cvt|1100|hp}} V-1710-59 engine with automatic boost control; 25 built.<ref name="WoF10p132">Dorr 1998, p. 132</ref><ref name="Angelucci and Bowers p.46">Angelucci and Bowers 1987, p. 46.</ref>

;P-39K
;;P-39K-1
:Bell Model 26A. Fitted with an Aeroproducts propeller and powered by a {{cvt|1325|hp}} V-1710-63 (E6) engine. 210 built.<ref name="bellp31"/><ref name="WoF10p132"/> 

;;P-39K-2
:Six conversion from P-39K-1 for ground attack and reconnaissance.<ref name="bellp31"/><ref name="Angelucci and Bowers p.46"/>

;;P-39K-5
:One conversion with a V-1710-85 (E19) engine to serve as a P-39N prototype.<ref name="WoF10p132"/>
[[File:P39 Nome Alaska LOC fsa 8e02409.jpg|thumb|P-39L-1BE 44-4673<br />Lend-Lease to USSR]]

;P-39L
;;P-39L-1
:Bell Model 26B, similar to P-39K with Curtiss Electric propeller and higher gross weight. 250 built.<ref name="bellp31"/><ref name="WoF10p132"/>

;;P-39L-2
:Eleven conversions from P-39L-1 for ground attack and reconnaissance.<ref name="bellp31"/><ref name="WoF10p132"/>
;P-39M
;;P-39M-1
:Bell Model 26D, variant with an {{cvt|11|ft|1|in}} Aeroproducts propeller, {{cvt|1200|hp}} V-1710-83 engine with improved high-altitude performance, {{cvt|10|mph}} faster than P-39L at {{cvt|15000|ft}}. 240 built.<ref name="bellp31"/>
;;P-39M-2
: Modification of P-39M-1 for ground attack/<ref name="bellp312">Pelletier 1992, pp. 31–32</ref>
;P-39N
:Bell Model 26N, originally part of the P-39G order. 1325&nbsp;hp V-1710-85 (E19) engine.<ref>{{cite web|url=http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=805 |title=Allison V-1710-85 & Drive Train for P-39Q |website=National Museum of the US Air Force |access-date=21 April 2016 |url-status=dead|archive-url=https://web.archive.org/web/20150303205724/http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=805 |archive-date=3 March 2015 }}</ref> {{cvt|10|ft|4|in}} Aeroproducts propeller and different reduction gear ratio. Starting with the 167th aircraft, the propeller diameter was increased to {{cvt|11|ft|7|in}} and internal fuel reduced from {{cvt|120|to|87|usgal}}; 500 built.
;;P-39N-1
:Variant with internal changes to adjust center of gravity when nose guns were fired; 900 built.

;;P-39N-2
:128 P-39N-1 converted with additional belly armor and cameras in rear fuselage.

;;P-39N-3B
:35 P-39N converted with additional belly armor and cameras in rear fuselage.

;;P-39N-5
:Variant with armor reduced from {{cvt|231|to|193|lb}}, Armor plate replaced the bulletproof glass behind the pilot, [[IFF Mark III|SCR-695]] radio was fitted, and a new oxygen system was installed; 695 built.

;;P-39N-6
:84 P-39N-5 converted with additional belly armor and cameras in rear fuselage.
[[File:P-39Q Cepinoga.jpg|thumb|Bell P-39Q Airacobra of the 508th Fighter Air Regiment of the Soviet Air Force, late 1944]]
;P-39Q
:The final production variant last one built in August 1944.

;;P-39Q-1
:Bell Model 26E,<ref name="bellp224" /> variant with wing-mounted .30 caliber machine guns replaced with a .50 caliber with 300 rounds of ammunition in a pod under each wing. Armor was increased to {{cvt|231|lb}}; 150 built.

;;P-39Q-2
:Five P-39Q-1s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.
[[File:P-39Q Airacobra.jpg|thumb|P-39Q-6BE ''Brooklyn Bum 2nd'' 71st TRG, 82nd FS<br />The Fighter Collection]]

;;P-39Q-5
:Production variant with reduced armor ({{cvt|193|lb}}), fuel capacity increased ({{cvt|110|usgal}}). Type A-1 bombsight adapters added; 950 built.

;;TP-39Q-5
:One conversion to a two-seat training variant with additional cockpit added in nose – no armament. Enlarged tail fillet and a shallow ventral fin added.

;;P-39Q-6
:148 P-39Q-5s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

;;P-39Q-10
:Variant with increased armor ({{cvt|228|lb}}), fuel capacity increased ({{cvt|120|usgal}}). Automatic Boost controls added and throttle and RPM controls coordinated. Winterization of oil systems and rubber mounts added to the engines; 705 built.

;;P-39Q-11
:Eight P-39Q-10s modified to carry cameras for photographic reconnaissance by adding K-24 and K-25 cameras in the aft fuselage.

;;P-39Q-15
:Production variant with reinforced inclined deck to prevent .50 caliber machine gun mounting cracking, bulkhead reinforcements to prevent rudder pedal wall cracking, a reinforced reduction gearbox bulkhead to prevent cowling former cracking, and repositioning of the battery solenoid. Oxygen system reduced from four bottle to two; 1,000 built.

;;P-39Q-20
:Production variant with minor equipment changes. The under-wing .50 caliber machine gun pods sometimes omitted; 1,000 built.

;;P-39Q-21
:109 P-39Q-20 fitted with a four-bladed Aeroproducts propeller.

;;RP-39Q-22
:12 P-39Q-20s converted to two-seat trainers.

;;P-39Q-25
:Production variant similar to the P-39Q-21 but with a reinforced aft-fuselage and horizontal stabilizer structure; 700 built.

;;P-39Q-30
:Production variant that reverted to the three-bladed propeller; 400 built.

;ZF-39
:Remaining examples in service, re-designated in June 1948.

;P-45
:The P-45 was the initial designation of the P-39C or Model 13.

;XFL-1 Airabonita
:One prototype tail-wheel undercarriage carrier fighter for the USN.

;XTDL-1
:[[United States Navy]] (USN) designation for two P-39Qs used as target drones.<ref>{{Cite book |last=Pelletier |first=Alain J. |url=https://archive.org/details/bell-aircraft/page/33/mode/2up?q=%22XTDL-1%22 |title=Bell Aircraft |publisher=Naval Institute Press |year=1992 |isbn=1-55750-056-8 |location=Great Britain}}</ref> Assigned to [[NAS Cape May]] for test work. Later redesignated ''F2L-1K''.

;F2L-1K
:XTDL-1 drones re-designated.

;P-400
:An export model of the P-39 with a less powerful cannon, using a 20 mm [[Hispano-Suiza HS.404|Hispano cannon]] rather than the standard 37&nbsp;mm cannon. It also had 2 .50 caliber machine guns in the nose, and 2 x .30 caliber machine guns in each wing.
 
;Airacobra I
:Bell Model 13, [[Royal Air Force]] (RAF) designation for three P-39Cs delivered to the [[A&AEE]] [[Boscombe Down]] for testing.

;Airacobra IA
:Bell Model 14. Briefly named ''Caribou''. 1,150&nbsp;hp V-1710-E4 engine, 1 × 20&nbsp;mm cannon with 60 rounds and 2 × .50 caliber machine guns mounted in the nose and four .303 caliber machine guns were mounted in the wings. [[Identification friend or foe|IFF]] set removed from behind pilot. note: the designation IA indicates direct purchase aircraft (as opposed to [[Lend-Lease]]); 675 built. The USAAF operated 128 former RAF aircraft with the designation P-400.

==Operators==
;{{AUS}}
* [[Royal Australian Air Force]]
;{{FRA}}
* [[Armée de l'Air]]
;{{flagcountry|Kingdom of Italy}}
* [[Italian Co-Belligerent Air Force]] operated 170 Bell P-39 Airacobra <ref>{{Cite web|url=http://www.aeroflight.co.uk/waf/italy/af/ital-af2-all-time.htm|title=Italian Air Force Aircraft Types|website=www.aeroflight.co.uk}}</ref>
;{{ITA}}
* [[Italian Air Force]] operated 102 surviving Bell P-39 Airacobra retired in 1950s
;{{POL}}
* [[Polish Air Force]] (One aircraft operated; personal aircraft of General Fyodor Polynin, Commander of the [[Polish Air Force]])
;{{POR}}
* [[Portuguese Air Force|Portuguese Army  Military Aeronautics]]: ''Esquadrilha Airacobra'' (Airacobra Squadron), later renamed ''Esquadrilha de Caça n.° 4'' (Fighter Squadron No. 4)
;{{USSR}}
* [[Soviet Air Forces]] (''Voyenno-Vozdushnye Sily'' or VVS)
* [[Soviet Naval Aviation]]
;{{UK}}
* [[Royal Air Force]]
* [[Royal Navy]] (Airacobra Mk 1 – test flight)
;{{USA}}
* [[United States Army Air Corps]] / [[United States Army Air Forces]]

==Surviving aircraft==

===Australia===
On display
P-39D
*41-6951 – Beck Military Collection in [[Mareeba, Queensland]].<ref>[http://www.pacificwrecks.com/aircraft/p-39/41-6951.html "P-39D Airacobra/41-6951"] ''pacificwrecks.com'' Retrieved: 4 March 2015.</ref>

===Canada===
Under restoration 
P-39M
*42-4725 – Under restoration at the [[Alberta Aviation Museum]] in [[Edmonton Alberta]].<ref>{{Cite web|url=https://albertaaviationmuseum.com/progress-continues-on-decade-long-p-39-joint-restoration-project/|title=Progress Continues On Decade Long P-39 Joint Restoration Project|date=4 November 2021}}</ref>

===Finland===
P-39Q
*44-2664 – The Anti Aircraft Museum in Tuusula. Plane was formerly placed in [[Aviation Museum of Central Finland]] in [[Tikkakoski]].<ref>[http://aerialvisuals.ca/LocationDossier.php?Serial=9666 "P-39Q Airacobra/44-2664"] ''aerialvisuals.ca'' Retrieved: 4 March 2015.</ref>

===Papua New Guinea===
P-39N
*42-19039 – J. K. McCarthy Museum in [[Goroka, Papua New Guinea]].<ref>[http://www.pacificwrecks.com/aircraft/p-39/42-19039.html "P-39N Airacobra/42-19039"] ''pacificwrecks.com'' Retrieved: 4 March 2015.</ref>

===Russia===
On display
P-39
*42537 – [[UMMC Museum Complex]], [[Verkhnyaya Pyshma]], Russia<ref>{{cite web | url=https://www.ugmk.com/press/news/v-muzee-voennoy-tekhniki-ugmk-poyavilas-legendarnaya-aerokobra/ | title=В музее военной техники УГМК появилась легендарная «Аэрокобра» | access-date=5 July 2023 | archive-date=5 July 2023 | archive-url=https://web.archive.org/web/20230705191124/https://www.ugmk.com/press/news/v-muzee-voennoy-tekhniki-ugmk-poyavilas-legendarnaya-aerokobra/ | url-status=dead }}</ref>
*220613 – House of Culture. Gagarin, [[Yakutsk]], Russia, {{cvt|450|km|order=flip}} south of the Arctic Circle<ref>{{Cite web|url=https://ssl.panoramio.com/photo_explorer#view=photo&position=1116&with_photo_id=83059705&order=date_desc&user=217417|archiveurl=https://web.archive.org/web/20130121082940/https://ssl.panoramio.com/photo_explorer|url-status=dead|title="P-39 Bell Aeorcobra/220613"|archivedate=21 January 2013}}</ref><ref>[https://www.panoramio.com/photo/2827228] {{Webarchive|url=https://web.archive.org/web/20171211053611/https://www.panoramio.com/photo/2827228|date=2017-12-11}} "P-39 Bell Aeorcobra/220613"</ref>

===United States===
'''Airworthy'''
P-39F
*41-7215 (unnamed) – [[Military Aviation Museum]] in [[Virginia Beach, Virginia]].<ref>[https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=39FF "FAA Registry: N39FF."] ''FAA Registry.'' Retrieved: 15 July 2021.</ref><ref>[https://militaryaviationmuseum.org/aircraft/wwii-aircraft/ "P-39F Airacobra/41-7215"]. ''Military Aviation Museum'' Retrieved: 21 September 2022.</ref>  Was restored by Pioneer Aero Ltd at Ardmore, Auckland, for Jerry Yagen. MSN 15-554<ref>[http://nzcivair.blogspot.com/2018/12/airacobra-zk-cob-update.html "Airacobra ZK-COB Update"] ''nzcivair.com'' Retrieved: 7 January 2019</ref> was forced to land near [[Weipa, Queensland]], on 1 May 1942, after running out of fuel. The aircraft remained abandoned at the site until recovery operations began in November 1971.<ref>[http://goodall.com.au/warbirds-directory-v6/bell.pdf "Warbird Directory: Bell"] Retrieved: 7 January 2019</ref> First flight at Ardmore by Frank Parker on 26 February 2019. Painted in USAAF colors as P-39Q-5-BE 42-20341 (Lend Lease to USSR) and now relocated to and flying with the Fighter Factory/MAM as of May 2019.<ref>{{cite magazine |title=News: P-39 flies in New Zealand |magazine=[[Aeroplane Monthly|Aeroplane]] |date=April 2019 |volume=47 |issue=4 |pages=6–7 |issn=0143-7240}}</ref>
P-39N
*42-8740 (unnamed) – [[Yanks Air Museum]] in [[Chino, California]].<ref>[https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=81575 "FAA Registry: N81575"] ''FAA.gov'' Retrieved: 15 July 2021.</ref><ref>[https://yanksair.org/collection/bell-26f-airacobra-p-39n-2/?_sf_s=p-39 "P-39N Airacobra/42-8740"] {{Webarchive|url=https://web.archive.org/web/20200726193731/https://yanksair.org/collection/bell-26f-airacobra-p-39n-2/?_sf_s=p-39 |date=26 July 2020 }} ''Yanks Air Museum'' Retrieved: 3 May 2017.</ref>
P-39Q
*42-19597 ''Miss Connie/Old Crow'' – [[Commemorative Air Force]] (CenTex Wing) in [[San Marcos, Texas]].<ref>[https://www.centraltexaswing.org/bell-p39 "P-39Q Airacobra/42-19597"] ''CAF CenTex Wing'' Retrieved: 3 July 2023.</ref><ref>[https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=6968 "FAA Registry: N6968"] ''FAA.gov'' Retrieved: 15 July 2021.</ref>
*42-19993 ''Brooklyn Bum'' – [[Lewis Air Legends]] in [[San Antonio]], [[Texas]].<ref>[https://www.lewisairlegends.com/p39-airacobra "P-39Q Airacobra/42-19993"] ''Lewis Air Legends'' Retrieved: 13 January 2020.</ref><ref>[https://registry.faa.gov/AircraftInquiry/Search/NNumberResult?nNumberTxt=139RL "FAA Registry: N139RL"] ''FAA.gov'' Retrieved: 15 July 2021.</ref>
'''On display'''
P-39N
*42-18814 ''Girlie'' – recovered from Tadji New Guinea in 1972 by MARC [[Pima Air & Space Museum]], adjacent to [[Davis-Monthan AFB]] in [[Tucson, Arizona]].<ref>[https://pimaair.org/museum-aircraft/bell-p-39n/ "P-39N Airacobra/42-18814"] ''Pima Air and Space Museum'' Retrieved: 16 March 2020.</ref>
*42-18408 ''Snooks 2nd / Betty Lou 3rd'' – [[Buffalo and Erie County Naval & Military Park]] in [[Buffalo, New York]].<ref>[https://buffalonavalpark.org/exhibits/museum/ "P-39N Airacobra/42-18408"] ''Buffalo & Erie County Naval & Military Park'' Retrieved: 12 September 2022.</ref>
P-39Q
*42-20000 (unnamed) – [[March Field Air Museum]] at [[March ARB]] (former [[March AFB]]) in [[Riverside, California]].<ref>[https://www.marchfield.org/aircraft/fighter/p-39q-airacobra-bell/ "P-39Q Airacobra/42-20000"]  ''March Field Air Museum'' Retrieved: 19 December 2017.</ref>
*42-20007 (unnamed) – [[Virginia Air & Space Center]] near [[Langley AFB]] in [[Hampton, Virginia]].<ref>[http://www.vasc.org/exhibit/aircraft/ "P-39Q Airacobra/42-20007"]  ''Virginia Air & Space Center'' Retrieved: 19 December 2017.</ref>
*44-2485 (unnamed) – [[Erickson Aircraft Collection]] in [[Madras, Oregon]].<ref>[http://www.ericksoncollection.com/aircraft/#/bell-p-39-airacobra/ "P-39Q Airacobra/44-2485"] ''Erickson Aircraft Collection'' Retrieved: 8 March 2015.</ref>
RP-39Q
[[File:Air Zoo December 2019 015 (Bell P-39Q Airacobra).jpg|thumb|P-39Q on display at the [[Air Zoo]]]]
*44-3887 (unnamed) – [[National Museum of the United States Air Force]] at [[Wright-Patterson AFB]] in [[Dayton, Ohio]].<ref>[https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196306/bell-p-39q-airacobra/ "RP-39Q Airacobra/44-3887"]  ''National Museum of the USAF'' Retrieved: 19 December 2017.</ref>
*44-3908 ''Whistlin Britches'' – [[Air Zoo]] in [[Kalamazoo, Michigan]].<ref>[https://www.airzoo.org/wwii#dismiss "RP-39Q Airacobra/44-3908"] ''Kalamazoo Aviation History Museum'' Retrieved: 16 March 2020.</ref>
'''Under restoration or in storage'''
P-39N
*42-19027 ''Small Fry/Little Sir Echo'' – under restoration for static display at [[Planes of Fame]] in [[Chino, California]].<ref>[https://planesoffame.org/aircraft "P-39N Airacobra/42-19027"] ''Planes of Fame Museum'' Retrieved: 13 January 2020.</ref>
P-39Q 
*44-2433 ''Galloping Gertie'' – in storage at the Paul Garber Facility of the [[National Air and Space Museum]] in [[Silver Hill, Maryland]].<ref>[http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19560019000 "P-39Q Airacobra/44-2433"] {{Webarchive|url=https://web.archive.org/web/20150906022714/http://airandspace.si.edu/collections/artifact.cfm?object=nasm_A19560019000 |date=2015-09-06 }} ''National Air and Space Museum'' Retrieved: 22 July 2014.</ref>
*44-2911 ''Miss Lend Lease'' – under restoration at the [[Niagara Aerospace Museum]] in [[Niagara Falls, New York]]. This plane was recovered from a Russian lake after disappearing during a routine mission during WWII. The pilot's remains were recovered and buried with full military honors. The aircraft crashed due to engine failure, as two holes were found inside the engine block from snapped connecting rods.<ref>[https://niagaraaerospacemuseum.org/collections/p-39-miss-lend-lease/ "P-39Q Airacobra/44-2911"] ''Niagara Aerospace Museum'' Retrieved: 12 September 2022.</ref>

==Specifications (P-39Q)==
[[File:Bell P-39D Airacobra.svg|thumb|Three-view drawing]]
[[File:P-39Q Airacobra.png|thumb|P-39Q at the [[National Museum of the US Air Force]]. This winter diorama shows ground crew with a Type F-1A utility heater in front of an Airacobra flown by Lt. L. Spoonts of the 57th FS based on Adak Island during the Aleutians Campaign in 1942.]]
{{Aircraft specs
|ref=Flight Operating Instructions P-39Q;<ref>{{Cite web|url=http://www.wwiiaircraftperformance.org/P-39/P-39Q-1_Operating_Instructions.pdf|title=Flight Operating Instructions P-39Q|access-date=27 September 2015|archive-date=14 December 2022|archive-url=https://web.archive.org/web/20221214165004/http://www.wwiiaircraftperformance.org/P-39/P-39Q-1_Operating_Instructions.pdf|url-status=dead}}</ref> Memorandum Report on P-39Q-5 Airplane<ref>{{Cite web|url=http://www.wwiiaircraftperformance.org/P-39/P-39Q-5_42-19615_ENG-19-1631-A.pdf|title=Memorandum Report on P-39Q-5 Airplane}}</ref>
|prime units?=imp
|crew=One
|length ft=30|length in=2
|span ft=34|span in=0
|height ft=12|height in=5
|wing area sqft=213
|airfoil=
|empty weight lb=6516
|gross weight lb=7570
|max takeoff weight lb=8400
<!--Powerplant-->
|eng1 number=1|eng1 name=[[Allison V-1710-85]]|eng1 type=V-12 liquid-cooled piston engine|eng1 hp=1200
|eng1 note=at {{cvt|9000|ft|0}} (emergency power)
|prop blade number=3|prop name=constant-speed propeller|prop dia ft=|prop dia in=
<!--Performance-->
|max speed mph=389
|stall speed mph=95
|stall speed note=power off, flaps and undercarriage down
|never exceed speed mph=525
|range miles=525
|range note=on internal fuel
|ceiling ft=35000
|climb rate ftmin=3805
|climb rate note=at {{cvt|7400|ft}} (using emergency power)
|time to altitude= {{cvt|15000|ft}} in 4 minutes 30 seconds, at {{cvt|160|mph}}
|wing loading lb/sqft=34.6
|power/mass={{cvt|0.16|hp/lb}}
<!--Armament-->
|guns=<br>
:* 1 × [[37x145mmR M4|37 mm]] [[M4 cannon]] firing through the propeller hub (compare [[engine gun]])
:* 2 × [[.50 BMG|.50 caliber]] [[Synchronization gear|synchronized]] [[M2 Browning|Browning M2 machine gun]]s, nose-mounted
:* 2 × .50 caliber Browning M2 machine guns on each wing
|bombs=Up to {{cvt|500|lb}} of bombs under wings and belly
}}

==See also==
{{Portal|Aviation}}
{{aircontent
|related=
* [[Bell XFL Airabonita]]
* [[Bell P-63 Kingcobra]]
* [[Bell P-76]]
|similar aircraft=
<!-- aircraft with similar role, era, and capability -->
* [[Curtiss P-40 Warhawk|Curtiss P-40]]
* [[Hawker Hurricane]]
* [[Koolhoven F.K.55]]
* [[Messerschmitt Bf 109]]
* [[Nakajima Ki 43]]
* [[Supermarine Spitfire]]
* [[Weiss Manfréd WM-23 Ezüst Nyíl]]
* [[Yakovlev Yak-1]]
|lists=
* [[List of aircraft of World War II]]
* [[List of military aircraft of the United States]]
* [[List of fighter aircraft]]
|see also=
}}

==References==

===Notes===
{{Reflist|group=N}}

===Citations===
{{Reflist}}

===Bibliography===
* ''AAHS Journal, American Aviation Historical Society,'' Volume 46, 2001.
* Angelucci, Enzo and Paolo Matricardi. ''World Aircraft: World War II, Volume II'' (Sampson Low Guides). Maidenhead, UK: Sampson Low, 1978. {{ISBN|0-562-00096-8}}.
* Angelucci, Enzo and Peter M. Bowers. ''The American Fighter: The Definitive Guide to American Fighter Aircraft from 1917 to the Present.'' New York, Orion Books, 1987. {{ISBN|0-517-56588-9}}.
* Bergström, Christer. ''Bagration to Berlin – The final Air Battle in the East 1944–45''. Hersham, UK: Classic Publications, 2008. {{ISBN|978-1-903223-91-8}}.
* Bodie, Warren. [https://books.google.com/books?id=KzHpAAAACAAJ ''The Lockheed P-38 Lightning.''] St. Paul, Minnesota: Widewing Publications, 1991. {{ISBN|0-9629359-5-6}}.
* Bowers, Peter M. "Airborne Cobra Pt. I". ''Airpower'', Vol. 8, No. 6, November 1978.
* Bowers, Peter M. "Airborne Cobra Pt. II". ''Airpower'', Vol.9, No. 1, January 1979.
* Brown, Captain Eric. ''Wings on My Sleeve''. London: Weidenfeld & Nicolson, 2006. {{ISBN|0-297-84565-9}}.
* Byk, Gary. ''The Modeller's Guide to the Bell P-39 Airacobra in RAAF Service''. Melbourne, Australia: Red Roo Models Publication, 1997. {{ISBN|0-646-32869-7}}.
* Dean, Francis H. ''America's Hundred Thousand''. Atglen, Pennsylvania: Schiffer Publishing Ltd, 1997. {{ISBN|0-7643-0072-5}}.
* Dial, Jay Frank. ''The Bell P-39 Airacobra, Aircraft in Profile no.165''. Windsor, Berkshire, UK: Profile Publications. Ltd., 1966 (reprinted 1971). No ISBN.
* "Dimensione Cielo aerei Italiani nella Seconda Guerra Mondiale." (in Italian) ''Caccia Assalto 3''. Rome: Edizioni Bizzarri, 1972.
* Donald, David. "Bell P-39 Airacobra." ''The Encyclopedia of World Aircraft''. Leicester, UK: Blitz Editions, 1997. {{ISBN|1-85605-375-X}}.
* Dorr, Robert F. "Bell Cobra Variants: Bell P-39 Airacobra and P-63 Kingcobra". ''Wings of Fame'', Volume 10, 1998. London: Aerospace Publishing. pp. 116–143. {{ISBN|1-86184-013-6}}. {{ISSN|1361-2034}}. 
* Dorr, Robert F. and Jerry C. Scutts. ''Bell P-39 Airacobra''. Ramsbury, Marlborough, Wiltshire, UK: The Crowood Press Ltd., 2000. {{ISBN|1-86126-348-1}}.
* Drabkin, Artem. ''The Red Air Force at War: Barbarossa and the Retreat to Moscow – Recollections of Fighter Pilots on the Eastern Front''. Barnsley, South Yorkshire, UK: Pen & Sword Military, 2007. {{ISBN|1-84415-563-3}}.
* Fitzsimons, Bernard, editor. "Airacobra, Bell P-39". ''The Illustrated Encyclopedia of 20th Century Weapons and Warfare, Volume 1''. New York: Columbia House, 1977. {{ISBN|0-8393-6175-0}}.
* Green, William. ''War Planes of the Second World War, Volume 4''. London: Macdonald & Co., 6th Edition, 1969. {{ISBN|0-356-01448-7}}.
* Green, William and Gordon Swanborough. ''WW2 Aircraft Fact Files:  U. S. Army Air Force Fighters, Part 1''. London: Macdonald and Jane's, 1977. {{ISBN|0-356-08218-0}}.
* Gueli, Marco. "Gli Airacobra Italiani" (in Italian). ''Storia Militare n.132'', September 2004.
* Gunston, Bill. ''Aircraft of World War 2''. London: Octopus Books Limited, 1980. {{ISBN|0-7064-1287-7}}.
* Hardesty, Von. ''Red Phoenix: The Rise of Soviet Air Power 1941–1945''. Washington, D.C.: Smithsonian Institution, 1991 (first edition 1982). {{ISBN|0-87474-510-1}}.
* Hoover, R.A. and Mark Shaw. ''Forever Flying''. New York: Pocket Books, 1996. {{ISBN|978-0-671-53761-6}}.
* Johnsen, Frederick A. ''Bell P-39/P-63 Airacobra & Kingcobra''. St. Paul, Minnesota: Voyageur Press, 1998. {{ISBN|1-58007-010-8}}.
* Johnson, Brian and Terry Heffernan. ''A Most Secret Place: Boscombe Down 1939–45''. London: Jane's Publishing Company Limited, 1982. {{ISBN|0-7106-0203-0}}
* Juszczak, Artur and Robert Pęczkowski. ''Bell P-39 Airacobra'' (in Polish). Sandomierz, Poland/Redbourn, UK: Mushroom Model Publications, 2003. {{ISBN|83-916327-9-2}}.
*Kelsey, Benjamin S. ''The Dragon's Teeth?: The Creation of United States Air Power for World War II.'' Washington, D.C.: Smithsonian Institution Press, 1982. {{ISBN|0-87474-574-8}}.
* Kinzey, Bert. ''P-39 Airacobra in Detail, D&S Vol. 63''. Carrollton, Texas: Squadron/Signal Publications, Inc., 1999. {{ISBN|1-888974-16-8}}.
*{{cite journal |last1=Kulikov|first1=Victor|title=Les "Cobras" soviétiques au combat |journal=Avions: Toute l'Aéronautique et son histoire |date=August 2000|issue=89 |pages=5–13 |trans-title=Soviet "Cobras" in Combat|language=fr |issn=1243-8650}}
*{{cite journal |last1=Kulikov|first1=Victor|title=Les "Cobras" soviétiques au combat |journal=Avions: Toute l'Aéronautique et son histoire |date=September 2000|issue=90 |pages=6–22 |language=fr |issn=1243-8650}}
* Lednicer, David A. "Aerodynamics of the Bell P-39 Airacobra and P-63 Kingcobra." ''SAE paper 2000-01-167.'' Warrendale, Pennsylvania: SAE International, 9 May 2000.
*{{cite journal |last1=Lopez|first1=Mario Canoniga|title=Fighters of the Cross of Christ |journal=Air Enthusiast |date=August–November 1990|issue=13|pages=13–25 |issn=0143-5450}}
* Loza, Dmitriy and James F. Gebhardt, editor and translator. ''Attack of the Airacobras: Soviet Aces, American P-39s & the Air War Against Germany''. Lawrence, Kansas: University Press of Kansas, 2002. {{ISBN|0-7006-1140-1}}.
* Mariinskiy, Evgeniy. ''Red Star Airacobra: Memoirs of a Soviet Fighter Ace 1941–45''. Solihull, UK: Helion and Company, 2006. {{ISBN|1-874622-78-7}}.
* Mason, Francis K. ''Royal Air Force Fighters of World War Two, Volume One''. Garden City, New York: Doubleday & Company Inc., 1971. {{ISBN|0-85064-012-1}}.
* Matthews, Birch. ''Cobra! Bell Aircraft Corporation 1934–1946''. Atglen, Pennsylvania: Schiffer Publishing, 1996. {{ISBN|0-88740-911-3}}.
* Mattioli, Marco. ''Bell P-39 Airacobra in Italian Service, Aviolibri Special 7'' (Bilingual Italian/English). Rome: IBN Editore, 2003. {{ISBN|88-86815-85-9}}.
* McDowell, Ernest. ''P-39 Airacobra in Action, Aircraft No.43''. Carrollton, Texas: Squadron/Signal Publications, Inc., 1980. {{ISBN|0-89747-102-4}}.
* Mellinger, George and John Stanaway. ''P-39 Airacobra Aces of World War 2''. Botley, Oxford, UK: Osprey Publishing, 2001. {{ISBN|1-84176-204-0}}.
* Mitchell, Rick. ''Airacobra Advantage: The Flying Cannon. The Complete Story of Bell Aircraft Corporation's P-39 Pursuit Fighter Plane''. Missoula, Montana: Pictorial Histories Publishing Co., 1992 (second printing 1995). {{ISBN|0-929521-62-5}}.
* Morgan, Hugh. ''Gli assi Sovietici della Seconda guerra mondiale'' (in Italian). Rome: Edizioni del Prado/Osprey Aviation, 1999. {{ISBN|84-8372-203-8}}
* Park, Edwards. ''Nanette, Her Pilot's Love Story''. Washington, D.C.: Smithsonian Institution Press, 1977. (2nd edition 1989). {{ISBN|0-87474-737-6}}.
* Pearcy, Arthur. ''Flying the Frontiers: NACA and NASA Experimental Aircraft.'' Annapolis, Maryland: Naval Institute Press, 1993. {{ISBN|1-55750-258-7}}.
* Pejčoch, Ivo. ''Bojové Legendy: P-39 Airacobra'' (in Czech). Prague, Czech Republic: Jan Vašut s.r.o., 2008. {{ISBN|978-80-7236-573-9}}.
* Pelletier, A. J. ''Bell Aircraft since 1935''. Annapolis, Maryland, USA: Naval Institute Press, 1992. {{ISBN|1-55750-056-8}}.
* Roman, Valerij. ''Aerokobry vstupayut v boy ('Airacobras enter combat'), Белл P-400, P-39D-1, P-39D-2 ("Avia-retro" series 1)'' (in Ukrainian). Kyiv, Ukraine: Aero-Hobby, 1993. {{ISBN|5-77075-170-3}}.
* Roman, Valerij. ''Aerokobry nad Kuban'yu (Airacobras over Kuban'), P-39 K, L и M ("Avia-retro" series 2)'' (in Ukrainian). Kyiv, Ukraine: Aero-Hobby, 2006. {{ISBN|0-9780696-0-9}}.
* Tomalik, Jacek. ''Bell P-39 Airacobra Cz.1, Monografie Lotnicze 58'' (in Polish). Gdańsk, Poland: AJ-Press, 1999. {{ISBN|83-7237-032-X}}.
* Tomalik, Jacek. ''Bell P-63 Kingcobra, XFL-1 Airabonita, P-39 Airacobra Cz.2, Monografie Lotnicze 59'' (in Polish). Gdańsk, Poland: AJ-Press, 2001. {{ISBN|83-7237-034-6}}.
* ''United States Air Force Museum Guidebook''. Wright-Patterson AFB, Ohio: Air Force Museum Foundation, 1975.
* Williams, Neil. ''Aerobatics''. New York: St. Martin's Press, 1975. {{ISBN|978-0-9504543-0-6}}.
* Wixey, Ken. "Flying Cannon: Bell's Cobra Family, Part One". ''Air Enthusiast'', No. 80, May–June 1999, pp.&nbsp;20–27. {{ISSN|0143-5450}}
* Woods, Robert J. "Why a Rear Engine Installation," Parts I and II. ''Aviation,'' March and April 1941.

==Further reading==
* Vernon, Jerry. "Round-Out: Canadian 'Cobras". ''Air Enthusiast'', No. 82, July–August 1999, pp.&nbsp;76–77. {{ISSN|0143-5450}}

==External links==
{{Commons category}}
* {{Internet Archive film clip|id=FlyingTheP-39|description=''Flying The P-39'', demonstrating techniques for piloting the P-39 Airacobra}}
* [https://www.awm.gov.au/collection/F10876/ Australian War Memorial, ''US 5th Airforce gun camera footage'', 1943]. Includes P-39 gun camera footage (from the 1:03 mark). Lt Robert Adler ([[41st Fighter Squadron|41st FS, USAAF]]) downing twin-engine Japanese bombers near [[Tsili Tsili Airfield|Tsili Tsili]], New Guinea, in 1943.

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[[Category:Bell aircraft|P-39]]
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[[Category:1930s United States fighter aircraft|Bell P-39]]
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