View source for Boeing 377 Stratocruiser

{{Short description|US airliner with 4 piston engines, 1947}}
{{Use mdy dates|date=June 2023}}
{{Use American English|date=June 2023}}
{{Infobox aircraft
 |name= Boeing 377 Stratocruiser
 |image= File:Pan Am Stratocruiser San Francisco.jpg{{!}}border
 |caption= A Pan Am Stratocruiser over San Francisco Bay
 |type = [[Airliner]]
 |national_origin= United States
 |manufacturer = [[Boeing Commercial Airplanes]]
 |designer=
 |first_flight= July 8, 1947
 |introduction= April 1, 1949, with [[Pan American World Airways]]
 |retired= 1963
 |number_built= 56<ref>{{cite web |url=http://www.boeing.com/history/products/model-377-stratocruiser.page |title=Boeing: Historical Snapshot: Model 377 Stratocruiser Commercial Transport |website=www.boeing.com}}</ref><ref>{{cite web |url=http://www.aviation-history.com/boeing/377.html |title=Boeing 377 Stratocruiser |website=www.aviation-history.com}}</ref>
 |status= 
 |primary_user= [[Pan American World Airways]] <!--Limit one (1) primary user-->
 |more_users  =[[BOAC]]<br />[[Northwest Airlines]]
 |developed_from= [[Boeing C-97 Stratofreighter]]
 |developed_into= [[Aero Spacelines Pregnant Guppy]]<br />[[Aero Spacelines Super Guppy]]<br />[[Aero Spacelines Mini Guppy]]
}}

The '''Boeing 377 Stratocruiser''' was a large long-range [[airliner]] developed from the [[Boeing C-97 Stratofreighter|C-97 Stratofreighter]] military transport, itself a derivative of the [[Boeing B-29 Superfortress|B-29 Superfortress]]. The Stratocruiser's first flight was on July 8, 1947.<ref name="Boeing Stratocruiser">{{cite web |url=http://www.boeing.com/history/boeing/m377.html |title=Boeing History: Stratocruiser Commercial Transport |publisher=Boeing.com |date=1947-07-08 |access-date=2012-06-18 |url-status=dead |archive-url=https://web.archive.org/web/20120606024948/http://www.boeing.com/history/boeing/m377.html |archive-date=June 6, 2012}}</ref> Design features included passenger decks and a [[Cabin pressurization|pressurized cabin]]. It could carry up to 100 passengers on the main deck plus 14 in the lower deck lounge; typical seating was for 63 or 84 passengers or 28 berthed and five seated passengers.

The Stratocruiser was larger than the [[Douglas DC-6]] and [[Lockheed Constellation]] and cost more to buy and operate. Its reliability was poor, mainly due to problems with the four 28-cylinder [[Pratt & Whitney R-4360 Wasp Major]] [[radial engine]]s and  structural and control problems with their propellers. Only 55 Stratocruisers were built for airlines, along with the single prototype. One was converted into the [[Aero Spacelines Pregnant Guppy]] by [[John M. Conroy]] for [[NASA]]’s [[Project Gemini|Gemini]] space program.

==Design and development==
[[File:Boeing 377 Factory.jpg|thumb|The Boeing 377 production line]]
[[File:Boeing 377 sleeping arrangements.jpg|thumb|upright|Berths and seating aboard a 377]]

The Boeing 377 Stratocruiser was a civil derivative of the Boeing Model 367, the [[Boeing C-97 Stratofreighter]], which first flew in late 1944. [[William McPherson Allen|William Allen]], who had become president of the Boeing Company in September 1945, sought to introduce a new civilian aircraft to replace reduced military production after [[World War II]].<ref>Redding and Yenne 1997, p. 68.</ref> Boeing saw in their large-bodied, fast, and long-ranged military transport potential for a passenger aircraft suited for premium service on long transoceanic routes, expanding on the precedent set by their [[Boeing 314 Clipper]] with [[Pan American World Airways]]. Despite a recession in late 1945, Allen ordered 50 Stratocruisers, spending capital on the project without an order from an airline customer.<ref name="Redding and Yenne 1997, p. 69">Redding and Yenne 1997, p. 69.</ref>

On November 29, 1945, [[Pan American World Airways]] (Pan Am) became the launch customer with the largest commercial aircraft order in history, a $24.5 million order for 20 Stratocruisers.<ref name="Redding and Yenne 1997, p. 69"/> Earlier in 1945, a [[Boeing C-97 Stratofreighter|Boeing C-97]] had flown from Seattle to Washington, D.C. nonstop in six hours and four minutes; with this knowledge, and with Pan Am President [[Juan Trippe]]'s  high regard for Boeing after their success with the [[Boeing 314 Clipper]], Pan Am was confident about ordering the expensive plane.<ref name="Redding and Yenne 1997, p. 69"/><ref>{{cite web |url=https://internationalaviationhq.com/2019/09/28/boeing-377-stratocruiser/ |title=Boeing 377 Stratocruiser: The Original Jumbo Jet? |last=Pask |first=Alexander |website=[[International Aviation HQ]] |date=28 September 2019}}</ref>

The 377 shared the distinctive design of the C-97, with a "double-bubble" fuselage cross-section, resembling a figure-8, with the smaller loop on the bottom, and {{convert|6600|cuft}} of interior space shared between two passenger decks. Outside diameter of the upper lobe was 132 inches, compared to 125 inches for the DC-6 and other Douglas types (and 148 inches for today's 737). The lower deck served as a lounge, seating 14. The 377 had innovations such as higher cabin pressure and air conditioning; the superchargers on the four Pratt & Whitney R-4360 engines increased power at altitude and allowed constant cabin pressure.<ref name="Redding and Yenne 1997, p. 71">Redding and Yenne 1997, p. 71.</ref>

The wing was the Boeing ''117'' airfoil. In all, 4 million man-hours went into the engineering of the 377.<ref name="Redding and Yenne 1997, p. 70">Redding and Yenne 1997, p. 70.</ref>  It was one of only a few [[double-deck aircraft]] ever built for commercial use, another being its French contemporary, the [[Breguet Deux-Ponts]], as well as later models, the [[Boeing 747|747]] and the [[Airbus A380]].

The first flight of the 377 was on July 8, 1947, two years after the first commercial order. The flight test fleet of three 377s underwent {{convert|250,000|smi|nmi km|-3|abbr=on}} of flying to test its limits before certification.<ref>{{cite book |title=Pushing the Envelope: The American Aircraft Industry |first=Donald M. |last=Pattillo |year=1998 |isbn=0472108697 |publisher=University of Michigan Press}}{{page needed|date=May 2015}}</ref>

Other carriers who adopted the Stratocruiser were [[British Overseas Airways Corporation]], [[American Overseas Airlines]] (merged with Pan Am in 1950) and [[United Airlines]].  The last 377 was delivered to BOAC in May 1950. On this delivery flight, Boeing engineer Wellwood Beall accompanied the final 377 to England, and returned with news of the [[de Havilland Comet]], the first jet airliner, and its appeal.<ref name="Redding and Yenne 1997, p. 71" />  The tenure of the Stratocruiser with United ended in 1954, when United had the opportunity to sell them to BOAC after finding them unprofitable without the extra mail subsidies enjoyed by Pan Am and Northwest.

Only 56 were built, one prototype (later reconditioned) and 55 production aircraft. As a result of low production volume, Boeing lost $7 million on the aircraft.<ref>{{cite book |last1=Simons |first1=Graham M. |title=Boeing 707 Group: A History |date=30 January 2018 |publisher=Pen and Sword |isbn=978-1-4738-6136-7 |url=https://books.google.com/books?id=7gTMDwAAQBAJ&dq=united+airline+executive+ray+ireland&pg=PT27 |language=en}}</ref>

==Operational history==
[[File:United 377 over Golden Gate.jpg|thumb|right|A [[United Airlines]] 377 over the [[Golden Gate Bridge]]]]
[[File:Boeing 377 Stratocruiser, BOAC.jpg|thumb|A [[British Overseas Airways Corporation|BOAC]] Stratocruiser]]
As the launch customer, Pan Am was the first to begin scheduled flights, from San Francisco to Honolulu in April 1949. At the end of 1949, Pan Am, [[BOAC]] and [[American Overseas Airlines]] (AOA) were flying 377s transatlantic, while [[Northwest Orient Airlines]] was flying in the United States; in January 1950, United began flights from San Francisco to Honolulu. Stratocruisers were pressed into emergency military service after the onset of the [[Korean War]].<ref name="gann" /> In late 1950, Northwest Stratocruisers were serving New York City, Chicago, Detroit, Minneapolis/St. Paul, Milwaukee, Spokane, Seattle, and Honolulu.<ref>http://www.timetableimages.com, Sept. 24, 1950 Northwest Orient timetable</ref>

By late 1952, Northwest Stratocruisers replaced [[Douglas DC-4|DC-4s]] to [[Tokyo]] via [[Anchorage, Alaska]];<ref>{{cite web |url=http://www.timetableimages.com/ttimages/complete/nw52/nw52-3.jpg |access-date=4 May 2023 |website=timetableimages.com |title=International Schedules}}</ref> Northwest replaced the Stratocruiser on the Honolulu run in 1953<ref>{{cite web |url=http://www.timetableimages.com/ttimages/nw/nw53/nw53-3.jpg |access-date=4 May 2023 |website=timetableimages.com |title=Complete Schedules}}</ref> and to Tokyo in 1955.<ref>{{cite web |url=http://www.timetableimages.com/ttimages/complete/nw55/nw55-4.jpg |access-date=4 May 2023 |website=timetableimages.com |title=Complete Schedules |archive-date=September 20, 2018 |archive-url=https://web.archive.org/web/20180920235010/http://www.timetableimages.com/ttimages/complete/nw55/nw55-4.jpg |url-status=dead}}</ref> For a short time, Pan Am 377s flew to [[Beirut, Lebanon]], but after 1954, no 377 was scheduled east of Europe or west of [[Singapore]]. In 1954, United Stratocruisers flew Los Angeles to Honolulu and between Seattle and San Francisco;<ref>http://www.timetableimages.com, Aug. 1, 1954 United timetable</ref> United's B377 flights to Honolulu were all first class. In 1955, BOAC 377s had 50 First Class seats (fare $400 one way New York to London) or 81 Tourist seats (fare $290).<ref>''Flight'' 28 October 1955 p671</ref>  In 1956, Pan Am 377s flew from Los Angeles and San Francisco to [[Sydney]] with stops at Honolulu, [[Canton Island]] and [[Suva]] (via [[Nadi Airport]] in [[Fiji]]).<ref>http://www.timetableimages.com, July 1, 1956 Pan American timetable</ref>

By 1958, Pan Am was operating the Stratocruiser between Seattle, [[Washington (state)|Washington]] and [[Fairbanks]], [[Juneau]] and [[Ketchikan]], Alaska and between Seattle and [[Whitehorse, Yukon|Whitehorse]], [[Yukon]].<ref>http://www.timetableimages.com, Jan. 1, 1958 Pan American timetable</ref> Within six years of first delivery, the Stratocruiser had carried 3,199,219 passengers; it had completed 3,597 transcontinental flights, and 27,678 transatlantic crossings, and went between the United States and South America 822 times. In these first six years, the Stratocruiser fleet had flown 169,859,579 miles (273,362,494&nbsp;km).<ref name="Redding and Yenne 1997, p. 71"/>

The 377 was one of the most advanced and capable propeller-driven transports, and among the most luxurious,<ref name="Redding and Yenne 1997, p. 70"/> but it was troubled by reliability issues and maintenance costs.  Problems included catastrophic failures of propellers, failures of propeller pitch control leading to [[overspeed]] incidents, issues related to the poor thermal design of the engine and resultant aerodynamic problems.<ref name=gann>{{cite web |url=http://www.ovi.ch/b377/articles/lady/ |title=Ernest K. Gann's Flying Circus: Lady with a past |publisher=Ovi.ch |access-date=2012-06-18}}</ref><ref name="Herken" /> Its service record was marred by a high incidence of in-flight emergencies and hull-loss accidents related to those issues.<ref name=Kuhns>{{cite web |url=http://enginehistory.org/Propellers/B377Props.pdf |author=Carl Kuhns |title=Boeing Model 377 Stratocruiser Propeller Woes |access-date=2018-03-18}}</ref> The propellers were the subject of [[Airworthiness Directives]] in 1955, 1957, and 1958.<ref name="Kuhns" /><ref name="Herken" />

In 1953, United's Chief Executive Ray Ireland described the aircraft as "unbeatable in luxury attraction but... uneconomical." Ireland said PAA's Stratocruiser competition to Hawaii induced United to buy the plane originally."<ref>''Aviation Week'' 31 August 1953, p.57.<!--title & author?--> The article discusses CAB rulings, and Ireland was perhaps speaking at a hearing.</ref> In 1950, United's seven 377s averaged $2.46 "direct operating cost" per plane-mile, and "Indirect costs are generally considered to be equal or greater than the direct costs."<ref>''American Aviation'' 23 July 1951 p37</ref> Most operators used Stratocruisers on long-range routes where higher prices could be charged, off-setting the higher operating costs.<ref>"Classic Airliners: Boeing Stratocruiser", p.64-67</ref>

The exception was Northwest Airlines, which managed to keep the aircraft competitive on shorter U.S. domestic routes where the aircraft's higher payload capacity benefited from lower fuel weights. United however could not integrate their six-plane fleet of 377s. By 1954, the lack of spares and the inability to cross-train their Douglas crews with the type relegated their Stratocruisers primarily to their Hawaii route, where they faced stiff competition from Pan American and Northwest. By the end of that year, the six United 377s were all sold to BOAC in a deal orchestrated by [[Douglas Aircraft]]. BOAC, which was short of aircraft following the grounding of the Comet 1, paid between US$895,000 and US$995,000 per unit and spares for what were essentially five-year-old aircraft. In 1954, an equivalent brand new [[Douglas DC-7]] cost US$775,000 (~${{Format price|{{Inflation|index=US-GDP|value=775000|start_year=1954}}}} in {{Inflation/year|US-GDP}}).<ref>"Airliner Tech Series, Vol. 9: Boeing 377Stratocruiser, p.60-61</ref>

Boeing set the never-exceed speed at {{convert|351|mph|kn km/h|abbr=on}} IAS but in testing, the 377 reached {{convert|409|mph|kn km/h|abbr=on}} IAS (about {{convert|500|mph|kn km/h||abbr=on}} TAS) in a 15–20 degree dive at {{convert|13,500|ft|abbr=on}};<ref>''American Aviation'' 8 January 1951, p.23.<!--title of the piece & author?--></ref> another report<ref>''The Aeroplane'' 15 October 1948</ref> said it reached {{cvt|498|mph|km/h}} true airspeed while diving from {{convert|21,000|ft|m}} altitude to {{convert|12,000|ft|m}} in 50 seconds using "full rated power". Typical airline cruise was less than {{convert|300|mph|kn km/h||abbr=on}}; in August 1953, Pan Am and United 377s (and United DC-6s) were scheduled between Honolulu and San Francisco ({{convert|2,398|mi|abbr=on}}) in 9&nbsp;h 45&nbsp;min each way.

The longest (by distance) 377 nonstop flights were made by Pan Am from Tokyo to Honolulu during four winter seasons beginning in 1952–1953. In January 1953, two nonstops a week were scheduled with a flight time of 11 hr 1 min due to tailwinds; the following August all flights took 19 hours, with a stop at [[Wake Island Airfield]]. In winter 1953-54, one Tokyo-Honolulu flight took 9 hr 35 min for {{convert|3853|mi|km|disp=preunit|great-circle |&nbsp;}}.<ref>''Aviation Week'' 15 Feb 1954 p100</ref>

By 1960, Stratocruisers were being superseded by jets: the [[de Havilland Comet]], [[Boeing 707]], and [[Douglas DC-8]].  The last flight of the 377 with United was in 1954, the last with BOAC was in 1959, and the last with Northwest was in September 1960. In November 1960, only a weekly Pan Am Honolulu to Singapore flight remained, and the 377 was retired by Pan Am in 1961.  High operating costs (notably the fuel consumption and maintenance of the Wasp Major engines) led to rapid abandonment of the 377 with the onset of the jet era.<ref name="gann" /> Its contemporaries such as the [[Douglas DC-6]] and the [[Lockheed Constellation]] continued longer, on secondary routes or rebuilt as freighters. A few 377s were sold to smaller airlines, used as freighters, or converted by [[Aero Spacelines]] into heavily modified enlarged freighters called [[Aero Spacelines Pregnant Guppy|Guppies]].<ref name="Wilson16">Wilson 1998, p. 16.</ref> 
[[File:377Transocean (4477474530).jpg|thumb|[[Transocean Air Lines|Transocean]] Boeing 377]]
During 1959 and 1960, [[Transocean Air Lines]] (TAL) assembled a fleet of fourteen at bargain prices.  In 1960, TAL went bankrupt and only four were in operable condition.  The hulks were stored at [[Oakland International Airport]] through the 1960s and cannibalized for parts, contributing some to the Aero Spacelines Guppies.<ref name="gann" /> Five remaining 377s were modified by Bedek Aviation to resemble former U.S. Air Force Model 367 Stratofreighters and pressed into service with the Israel Defense Forces. Two were shot down during the course of their service and the three remaining 377Ms were retired in 1978 and later scrapped. None of the 56 377s built were preserved for display in original condition, although one airframe remains today as the [[Aero Spacelines Mini Guppy|Mini Guppy]]; the [[Israeli Air Force Museum|IAF Museum]] in Israel has a C-97 (4X-FPM) on display painted to resemble their most famous 377M, ''Masada''.

==Variants==
;377-1
:Proposed variant to be powered by [[Wright R-3350 Duplex-Cyclone]] engines.  It was to be fitted with the flaps and [[deicing boot]]s from the B-29.<ref name=":1">Veronico, p.17</ref>
;377-6
:Proposed variant to be powered by supercharged [[Allison V-3420]] engines.<ref name=":1" />
;377-10-19
:Prototype Stratocruiser; one built. Later brought up to 377-10-26 standard and sold to [[Pan Am|Pan American World Airways]] in 1950.<ref name=":1" />
;377-10-26
:Variant built for Pan American World Airways with round windows.<ref name=":3">Veronico, p.30</ref>  20 new aircraft built, plus one converted from the 377-10-19 prototype.<ref name=":4">Bowers, p.367</ref>
;377-10-26S Super Stratocruiser
:10 refitted with more powerful engines and a larger fuel capacity for Pan American transatlantic flights.<ref name=":4" />
;377-10-27
:Variant intended for [[Trans World Airlines|Transcontinental & Western Air]], but not built.<ref name=":03"/>
;377-10-28
:Four ordered by the [[Scandinavian Airlines System]], but taken up by BOAC after SAS canceled the order.  Aircraft had circular windows and extra deluxe interior appointments, which differed with each aircraft.<ref name=":3" /><ref>Bowers, p.367–368</ref>
;377-10-29
:Eight delivered to [[American Overseas Airlines]] with round windows for the main cabin and rectangular windows for the lower cabin.<ref name=":3" /><ref name=":5">Bowers, p.368</ref>
;377-10-30
:Ten for [[Northwest Airlines|Northwest Orient Airlines]] with all rectangular windows.<ref name=":3" />  The aircraft were eventually fitted with weather radomes similar to the C-97A.<ref name=":5" />
;377-10-32
:Six for the [[British Overseas Airways Corporation]] (BOAC). All cabin windows were circular.<ref name=":3" /><ref name=":6">Bowers, p.370</ref>
;377-10-34
:Seven for [[United Airlines|United Air Lines]]. Rectangular windows on the main cabin and circular windows on the lower cabin.<ref name=":3" />  Six aircraft were later sold to BOAC.<ref name=":6" />
;377-10-40
:Proposed variant for domestic flights with high-density seating.  Was to be offered in a 105-seat "A" configuration or a 104-seat "B" configuration, both with only two lavatories and no galley.<ref>Veronico, p.19</ref>
;377-11
:Proposed variant to be powered by [[Wright XA-395]] turbine engines.<ref name=":1" />
;377-17-39
:Proposed variant for [[Cubana de Aviación]] to be powered by four [[Allison T40|Allison XT40-A-6]] turboprop engines, each driving two three-bladed [[contra-rotating propellers]].  The fuselage was to be stretched by {{Convert|80|in|cm|abbr=on}} forward and {{Convert|40|in|cm|abbr=on}} aft of the wing, and the gross weigh would have been increased to {{Convert|153000|lb|kg|abbr=on}}.  133 or 137 passengers would have been seated in an ultra-high density configuration.<ref name=":2">Veronico, p.16</ref><ref>{{Cite book |last=Dean |first=William Patrick |title=Ultra-Large Aircraft, 1940-1970: The Development of Guppy and Expanded Fuselage Transports |publisher=[[McFarland & Company]] |year=2018 |isbn=978-1476665030 |pages=134}}</ref>
;377-28-26
:Proposed six-engined variant for Pan American World Airways.  It was to be powered by two [[Wright R-1820 Cyclone]] engines mounted outboard of the four standard R-4360s, and it would have carried two external fuel tanks from the B-50.  Seating would have been identical to that of the 377-10-26.<ref name=":2" />
;377-212
:Proposed variant with a twin-deck all-economy cabin configuration.  The main deck was to seat 72 passengers, while the lounge deck would have been offered in a 22-seat "A" configuration or a 14-seat "B" configuration.<ref name=":1" />
;377F
:Freighter conversion.{{Citation needed|date=August 2024}}
;377M
[[File:Boeing B-377M Stratocruiser Anak (468952508).jpg|thumb|C-97 painted to represent a 377M ''Anak'', Israeli Air Force Museum (2007)]]
:In the early 1960s, the [[Israeli Air Force]] wanted to upgrade to the C-130 Hercules, which could lift larger payloads, but it was expensive and sales were embargoed by the United States. [[Israel Aircraft Industries]] at Ben Gurion International Airport offered to modify Boeing 377 Stratocruisers. It had a stronger cabin floor which could handle cargo, plus a C-97 military Stratocruiser tail section, which included a [[Clamshell design|clamshell]] cargo door. These were dubbed ''[[Anak]]'' (or Giant in Hebrew) and entered service in 1964. Three of these were modified by the use of a swing tail section, similar to the [[Canadair CC-106 Yukon|Canadair CL44D-4]] airliner. Two others served as aerial tankers with underwing hose reel refueling pods. Two others were ELINT-platforms for electronic reconnaissance, surveillance and [[electronic countermeasure]] (ECM) missions. These were later joined by four KC-97Gs with the flying boom system.

===Aero Spacelines Guppy===
[[File:Pregnant Guppy NASA.jpg|thumb|The Pregnant Guppy heavy lifter]]
[[File:Boeing 377-SG Super Guppy.jpg|thumb|The turbine-powered [[Aero Spacelines Super Guppy|Super Guppy]] of NASA]]
In addition to the Israeli Anaks, a company called [[Aero Spacelines]] was converting old 377s to aircraft called Guppies in the 1960s. There were three types: the Pregnant Guppy, Super Guppy, and Mini Guppy.<ref name="Boeing Stratocruiser" /> They had an extension to the top of the fuselage to enable them to carry large aircraft parts between manufacturing sites.
<!--were designed to carry outsize transports that could hold either a massive amount of cargo, or several decks of passengers. The main feature of the modifications was the huge dome-like expansion of the top of the original Stratocruiser fuselage.-->

The first was the [[Aero Spacelines Pregnant Guppy|Pregnant Guppy]], followed by the [[Aero Spacelines Super Guppy|Super Guppy]], and finally the [[Aero Spacelines Mini Guppy|Mini Guppy]]. The Super Guppy and the Mini Guppy had [[turboprop]] engines.

;Aero Spacelines 377PG Pregnant Guppy
:Conversion of one 377-10-26, incorporating an enlarged upper deck and a fuselage lengthened by 16 feet to carry sections of the [[Saturn V]] rocket. One converted.
;Aero Spacelines 377SG Super Guppy
:A single heavy-lift transport similar to the Pregnant Guppy built by Aero Spacelines. The aircraft contained parts of a YC-97J Stratofreighter and a 377-10-26 mated with a larger main fuselage, larger tail and [[Pratt & Whitney T34]] turboprops.
;Aero Spacelines 201 Super Guppy Turbine
:Originally designated the 377SGT, it was similar to the 377SG, but with a more aerodynamic fuselage, a [[Boeing 707]] nosewheel, wingspan stretched by {{convert|23|ft|m}}, and four [[Allison T56|Allison 501-D22C]] turboprops.<ref name=":03">{{Cite book |last=Simpson |first=R. W. |url=https://www.worldcat.org/title/ocm40588036 |title=Airlife's commercial aircraft and airliners |date=1999 |publisher=Airlife |isbn=978-1-84037-073-7 |location=Shrewsbury, England |oclc=ocm40588036}}</ref> Four were built and were used by Airbus to carry aircraft parts between its factories. In the 1990s, Airbus retired them due to rising operational costs and they have been replaced with [[Airbus Beluga]]s. Two of the former Airbus Industrie Super Guppies remain in Germany and France, with a third being scrapped in December 2020 after eleven years of restoration at [[Bruntingthorpe Aerodrome]] in the UK.<ref>{{cite web |url=https://www.scramble.nl/civil-news/the-end-of-bruntingthorpe-s-super-guppy |title=The end of Bruntingthorpe's Super Guppy |access-date=2021-05-16 |date=2020-11-28 |website=scramble.nl}}</ref> The fourth aircraft was acquired by NASA as part of a barter agreement with ESA for its role as a partner with the International Space Station.

;Aero Spacelines 377MG Mini Guppy
:Conversion of a 377-10-26, it featured a larger main cabin for oversize cargo, stretched wing and a hinged tail.<ref name=":03"/>
;Aero Spacelines 101 Mini Guppy Turbine
:Originally designated the 377MGT. Similar to the 377MG, but powered by [[Pratt & Whitney T34|Pratt & Whitney T34-PWA]] turboprop engines. Two built.<ref name=":03"/>

==Operators==
[[File:377Transocean (4477474530).jpg|thumb|[[Transocean Airlines]]]]
[[File:B377unitedSFO (4399853204).jpg|thumb|[[United Airlines]]]]
[[File:Juan Trippe with Stratocruiser.jpg|thumb|upright|Pan Am President [[Juan Trippe]] in front of a 377]]

'''{{ECU}}'''
* [[Línea Internacional Aérea]]
{{GHA}}

* [[Ghana Airways]] (Leased from BOAC)

'''{{GBR}}'''
* [[British Overseas Airways Corporation]] (BOAC)

'''{{ISR}}'''
* [[Israeli Air Force]]

'''{{NGA}}'''
* [[Nigeria Airways]] (Leased from BOAC)

'''{{SWE}}'''
* [[Svensk Interkontinental Lufttrafik]], part of [[Scandinavian Airlines System]] (aircraft not delivered - passed to BOAC)

'''{{USA}}'''
* [[American Overseas Airlines]]
* [[DAI Airways]]
* [[Northwest Airlines|Northwest Orient Airlines]]
* [[Pan American World Airways]]
* [[Transocean Airlines|Transocean Air Lines]]
* [[United Airlines]]

'''{{VEN}}'''
* [[RANSA|Rutas Aéreas Nacionales SA]]

==Accidents and incidents==
This aircraft type suffered 13 hull-loss accidents between 1951 and 1970 with a total of 139 fatalities. The worst single accident occurred on April 29, 1952.  The aircraft type also experienced a significantly high rate of in-flight emergencies related to engine and propeller failure, resulting in [[Airworthiness Directives]].<ref name="Kuhns" /><ref name=Herken>{{cite magazine |last1=Herken |first1=Gregg |last2=Fortenberry |first2=Ken |title=The Mystery of the Lost Clipper |magazine=[[Air & Space Magazine|Air & Space]] |url=http://www.airspacemag.com/history-of-flight/the-mystery-of-the-lost-clipper-5467157/ |date=September 2004 |access-date=February 3, 2014}}</ref>

Faults included structural failures of [[neoprene]]-cored propellers, failures of propeller pitch control resulting in [[overspeed]], and failures related to engine cooling.  Six propeller failures between 1950 and 1955 resulted in separation or near-separation of engines from mounts, with two resulting in hull-loss accidents.  Directives were issued in 1950, 1955, and 1958 regarding enhanced maintenance and fault detection, in-flight vibration monitoring, and propeller replacement.<ref name="Kuhns" />

A Directive concerning the pitch control system was issued after the October 16, 1956 hull-loss accident.  A June 1957 overspeed incident occurred on ''Romance of the Skies'', after the compliance date of the Directive and less than six months before its fatal accident of November 8, 1957.<ref name="Herken" />  No hull-loss accidents after the loss of the ''Romance'' have been attributed to an overspeed incident.<ref>{{Cite web |url=https://aviation-safety.net/database/types/Boeing-377-Stratocruiser/database |title=Aviation Safety Network > ASN Aviation Safety Database > Type index > ASN Aviation Safety Database results}}</ref>

; September 12, 1951
: [[United Airlines|United Air Lines]] Flight 7030, a Stratocruiser 10-34 (N31230, named ''Mainliner Oahu''), was being used for a semi-annual instrument check of a captain. At 11:39 PDT, the flight was cleared for an ILS approach to the San Francisco Airport. The aircraft, with No. 4 propeller feathered, stalled and abruptly dived from an altitude of approximately 300 feet and was destroyed upon impact in San Francisco Bay. All three crew aboard were killed. The probable cause was an inadvertent stall at low altitude.<ref>{{ASN accident|title= N31230|id= 19510912-1|access-date=2013-11-17}}</ref>
; April 29, 1952
: [[Pan Am Flight 202]], a Stratocruiser 10-26 (N1039V, named ''Clipper Boa Esperança'' aka Clipper Good Hope) en route from [[Ministro Pistarini International Airport|Buenos Aires-Ezeiza]] and [[Rio de Janeiro–Galeão International Airport|Rio de Janeiro–Galeão]] to [[New York City|New York]] via [[Piarco International Airport|Port of Spain]] crashed in the jungle in the south of the State of [[Pará]]. Probable causes are the separation of the second engine and propeller from the aircraft due to highly unbalanced forces followed by uncontrollability and disintegration of the aircraft. All 50 passengers and crew died in the worst-ever accident involving the Boeing 377.<ref>{{ASN accident|title= N1039V|id= 19520429-1|access-date=2011-09-15}}</ref>
; July 27, 1952
: [[Pan American World Airways|Pan Am]] Flight 201, a Stratocruiser 10-26 (N1030V) en route from [[New York City|New York]] and [[Rio de Janeiro–Galeão International Airport|Rio de Janeiro-Galeão]] to [[Ministro Pistarini International Airport|Buenos Aires-Ezeiza]] suffered explosive decompression at about 12,000 feet about 20 miles south of Rio de Janeiro. A passenger was blown out and the cabin considerably damaged, but the aircraft was able to return to Rio de Janeiro and make a safe landing. The main cabin door had not been properly locked.<ref>{{ASN accident|title= N1030V|id= 19520727-1|access-date=2011-09-24}}</ref><ref>{{cite news |title=Fall from plane kills L.A. woman |url=https://www.newspapers.com/article/the-los-angeles-times-fall-from-plane-ki/168804503/ |access-date=8 March 2022 |work=[[Los Angeles Times]] |date=28 July 1952 |location=Los Angeles, California |page=1 |via=[[Newspapers.com]]}}</ref>
; December 25, 1954
: A [[British Overseas Airways Corporation|BOAC]] Stratocruiser 10-28 (G-ALSA, named ''RMA Cathay'') [[1954 Prestwick air disaster|crashed]] on landing at [[Prestwick Airport|Prestwick]] at 0330 hours, killing 28 of the 36 passengers and crew on board. The aircraft had been en route from London to [[New York City]], when, on approach to Prestwick, it entered a steep descent before leveling-out too late and too severely, hitting the ground short of the runway.<ref>{{ASN accident|title= G-ALSA|id= 19541225-0|access-date=2010-11-18}}</ref>
; March 26, 1955
: [[Pan Am Flight 845/26]], a Stratocruiser 10-26 (N1032V, named ''Clipper United States''), [[Water landing|ditched]] 35 miles (56&nbsp;km) off the Oregon coast after the no. 3 engine and propeller tore loose from the wing, causing severe control difficulties. The aircraft sank after 20 minutes in water of about 1,600&nbsp;m (5,200&nbsp;ft) depth. There were four fatalities out of the 23 occupants, including two of the crew.
; April 2, 1956
: [[Northwest Orient Airlines Flight 2]], a Stratocruiser 10-30 (N74608, named ''Stratocruiser Tokyo''), ditched into [[Puget Sound]] after the flight engineer mistakenly failed to close the cowl flaps on the plane's engines, an error attributed to confusing instrument layout. Although all aboard escaped the aircraft after a textbook ditching, four passengers and one flight attendant succumbed either to [[drowning]] or to [[hypothermia]] before being rescued.
; October 16, 1956
: [[File:561016PanAmDitches-3.jpg|right|thumb|[[Pan Am Flight 6]] ditches near Hawaii]] [[Pan Am Flight 6]], a Stratocruiser 10-29 (N90943, named ''Clipper Sovereign of the Skies''), ditched northeast of Hawaii during the last leg of an around-the-world flight from [[Philadelphia]] to [[San Francisco]] after two of its four engines failed following an overspeed incident.<ref name="Herken" /> The aircraft was able to circle around [[USCGC Pontchartrain (WHEC-70)|USCG ''Pontchartrain'']] until daybreak, when it ditched; all 31 on board survived.
; November 8, 1957
: [[Pan Am Flight 7]], a Stratocruiser 10-29 (registered N90944, named ''Clipper Romance of the Skies''), left San Francisco for Hawaii with 38 passengers and six crew. The 377 crashed around 5:25&nbsp;p.m. in the Pacific Ocean. There were no survivors and the entire wreckage has never been found. Only 19 bodies and bits of debris were recovered. There is speculation that two passengers had a motive to bring the plane down. Eugene Crosthwaite, a 46-year-old purser, had shown blasting powder to a relative days prior to the flight, and had cut a stepdaughter from his will only one hour before the flight.  Pan Am concluded that there was sufficient evidence that Crosthwaite was the culprit.  William Payne, an ex-Navy demolitions expert, had taken out large insurance policies on himself just before the flight, and had a $10,000 debt he was desperate to pay off. The insurance investigator later suspected him of never being on the plane. His wife received at least $125,000 in payouts.  It was the opinion of the flight engineer during the ''Sovereign'' incident, and a pilot who had experienced an overspeed on the ''Romance'' less than six months before its loss, that an overspeed was a likely cause of the crash. The overspeed theory calls into question whether Pan Am was in compliance with an [[Airworthiness Directive]] concerning a weakness in the pitch control system, issued in response to the ''Sovereign'' incident the previous year.<ref name="Herken" />
; June 2, 1958
: A Pan Am Stratocruiser 10-26 (registration N1023V, named ''Clipper Golden Gate'') was on a flight from San Francisco to Singapore via several intermediate stops. As the aircraft touched down at Manila (runway 06) in a heavy landing in rainy and gusty conditions, the undercarriage collapsed as a result of the hard landing. The plane skidded and swerved to the right, coming to rest 2,850 feet past the runway threshold and 27 feet from the edge of the runway. One of the passengers was killed when one of the blades of the number 3 propeller broke off, penetrating the passenger cabin.<ref>{{ASN accident|title= N1023V|id= 19580602-0|access-date=2013-11-17}}</ref>
; April 10, 1959
: At the conclusion of a flight from Seattle to Juneau, Alaska, a Pan Am Stratocruiser 10-26 (N1033V, named ''Clipper Midnight Sun'') undershot on final approach and collided with an embankment. The aircraft caught fire and was destroyed, but all 10 passengers and crew survived.<ref>{{ASN accident|title= N1033V|id= 19590410-0|access-date=2013-11-17}}</ref>
; July 9, 1959
: A Pan Am Boeing Stratocruiser 10-29 (N90941, named ''Clipper Australia'') belly landed at [[Haneda Airport]] following landing gear problems; all 59 passengers and crew on board survived, but the aircraft was written off.<ref>{{ASN accident|title= N90941|id= 19590709-0|access-date=2013-11-17}}</ref>
; August 1967
: An [[Aero Spacelines]] Stratocruiser 10-29 (N90942) suffered a ground collision with Stratocruiser 10-32 N402Q at Mojave, California; the aircraft was damaged beyond repair.<ref>{{ASN accident|title= N90942|id= 19670899-0|access-date=2013-11-17}}</ref>
; May 12, 1970
: An Aero Spacelines 377MGT (N111AS) was being test flown following conversion from a Boeing 377. During the sixth takeoff with one engine shut down, the aircraft turned and rolled to the left. The left wingtip then struck the ground and the aircraft yawed severely after which the forward fuselage struck the ground, destroying the cockpit. All four crew died.<ref>{{ASN accident|title= N111AS|id= 19700512-0 | access-date=2013-11-17}}</ref>

==Specifications (377)==
[[File:Cockpit of a Boeing 377.jpg|alt=This is the cockpit of a Boeing 377. It does not include the stations of the navigator and flight engineer. You have yokes, rudder pedals, thrust levers, and a lot of "steam gauges", as is typical for this era of aircraft.|thumb|Cockpit of a Boeing 377.]]
{{Aircraft specs
|ref=Airliners of the World<ref>{{cite book |last=Wilson |first=Stewart |year=1999 |title=Airliners of the World |url=https://archive.org/details/airlinersofworld0000wils |url-access=registration |publisher=Fyshwick, Australia: Aerospace Publications |isbn=1-875671-44-7}}</ref>
|prime units?=imp
<!--
        General characteristics
-->
|crew= 4 flight crew (captain, first officer, flight engineer, navigator) + 2-3 cabin crew
|capacity=Up to 100 passengers on main deck plus 14 in lower deck lounge; typical seating for 63 or 84 passengers or 28 berthed and five seated passengers.
|length ft=110
|length in=4
|length note=
|span ft=141
|span in=3
|span note=
|upper span ft=
|upper span in=
|upper span note=
|mid span ft=
|mid span in=
|mid span note=
|lower span ft=
|lower span in=
|lower span note=
|swept ft=<!-- swing-wings -->
|swept in=<!-- swing-wings -->
|swept note=
|dia ft=<!-- airships etc -->
|dia in=<!-- airships etc -->
|dia note=
|width ft=<!-- if applicable -->
|width in=<!-- if applicable -->
|width note=
|height ft=38
|height in=3
|height note=
|wing area sqft=1769
|wing area note=
|swept area sqft=<!-- swing-wings -->
|swept area note=
|volume ft3=<!-- lighter-than-air -->
|volume note=
|aspect ratio=<!-- sailplanes -->
|airfoil=<!--'''root:''' [[NACA airfoil|NACA]]; '''tip:''' [[NACA airfoil|NACA]]<ref name="Selig">{{cite web |last1=Lednicer |first1=David |title=The Incomplete Guide to Airfoil Usage |url=https://m-selig.ae.illinois.edu/ads/aircraft.html |website=m-selig.ae.illinois.edu |access-date=16 April 2019}}</ref>-->
|empty weight lb=83500
|empty weight note=
|gross weight lb=
|gross weight note=
|max takeoff weight lb=148000
|max takeoff weight note=
|fuel capacity=
|lift lb=<!-- lighter-than-air -->
|lift note=
|more general=
<!--
        Powerplant
-->
|eng1 number=4
|eng1 name=[[Pratt & Whitney R-4360-B6 Wasp Major]]
|eng1 type=28-cylinder air-cooled radial piston engines
|eng1 hp=3500

|prop blade number=4
|prop name=constant-speed fully-feathering propellers
|prop dia ft=<!-- propeller aircraft -->
|prop dia in=<!-- propeller aircraft -->
|prop dia note=
<!--
        Performance
-->
|max speed mph=375
|max speed note=
|cruise speed mph=301
|cruise speed note=
|stall speed mph=
|stall speed note=
|never exceed speed mph=
|never exceed speed note=
|minimum control speed mph=
|minimum control speed note=
|range miles=4200
|range note=
|combat range miles=
|combat range note=
|ferry range miles=
|ferry range note=
|endurance=<!-- if range unknown -->
|ceiling ft=32000
|ceiling note=
|g limits=<!-- aerobatic -->
|roll rate=<!-- aerobatic -->
|climb rate ftmin=
|climb rate note=
|time to altitude=
|wing loading lb/sqft=
|wing loading note=
|fuel consumption lb/mi=
|power/mass=
|more performance=
<!--
        Armament
-->
}}

==See also==
{{Aircontent
|see also=

|related=
* [[Aero Spacelines Pregnant Guppy]]
* [[Aero Spacelines Super Guppy]]
* [[Aero Spacelines Mini Guppy]]
* [[Boeing B-50 Superfortress]]
* [[Boeing C-97 Stratofreighter]]
* [[Boeing KC-97 Stratofreighter]]
|similar aircraft=
* [[Canadair CL-44]]
* [[Boeing B-29 Superfortress]]
* [[Douglas DC-7]]
* [[Lockheed L-188 Electra]]
* [[Lockheed Constellation]]
* [[Lockheed L-049 Constellation]]
* [[Lockheed L-649 Constellation]]
* [[Lockheed L-749 Constellation]]
* [[Lockheed L-1049 Super Constellation]]
* [[Lockheed L-1649 Starliner]]
* [[Lockheed R6V Constitution]]
* [[Tupolev Tu-70]]
|lists=
}}

==Notes==
{{Reflist|30em}}

==Further reading==
* {{cite book |last=Bowers |first=Peter M. |title=Boeing Aircraft Since 1916 |year=1968 |publisher=Naval Institute Pres |location= |edition=2nd |isbn=0-87021-037-8}}
* ''Air Disaster, Vol. 4: The Propeller Era'', by [[Macarthur Job]], Aerospace Publications Pty. Ltd. (Australia), 2001 {{ISBN|1-875671-48-X}}
* {{cite book |last1=Redding |first1=Robert |last2=Yenne |first2=Bill |name-list-style=amp |title=Boeing: Planemaker to the World |date=1997 |publisher=Thunder Bay Press |location=San Diego, California |isbn=1-57145-045-9 |pages=68–71 |ref=none}}
*{{cite magazine |last=Taylor |first=H. A. "Tony" |title=Stratocruiser... Ending an Airline Era |magazine=[[Air Enthusiast]] |date=April–July 1982 |issue=18 |pages=37–53 |issn=0143-5450 |ref=none}}
* {{Cite book |last=Veronico |first=Nicholas A. |title=Boeing Model 377 Stratocruiser |publisher=Specialty Press Publishers and Wholesalers |year=2001 |isbn=1-58007-047-7}}
* {{cite book |last=Wilson |first=Stewart |year=1999 |title=Airliners of the World |url=https://archive.org/details/airlinersofworld0000wils |url-access=registration |publisher=Fyshwick, Australia: Aerospace Publications |isbn=1-875671-44-7 |ref=none}}
* {{cite book |last=Wilson |first=Stewart |year=1998 |title=Boeing 707, Douglas DC-8 & Vickers VC-10 |publisher=Fyshwick, Australia: Aerospace Publications |isbn=1-875671-36-6 |ref=none}}

==External links==
{{Commons and category|Boeing 377}}
* [http://www.ovi.ch/b377/index.html Boeing 377 – Stratocruiser] A very comprehensive enthusiast page on the type
* [http://www.aviation-history.com/boeing/377.html The Aviation History On-Line Museum – Boeing 377 Stratocruiser]
* [http://www.calclassic.com/b377.htm California Classic – The Boeing Model 377 Stratocruiser]
* [http://www.ovi.ch/b377/articles/boeingUnited/ Stratocruiser article excerpts]
* [http://www.israeli-weapons.com/weapons/aircraft/anak/Anak.htm Anak (Israeli Boeing 377)]
* [http://www.flightglobal.com/pdfarchive/view/1949/1949%20-%200159.html "Speedbird Stratocruiser: A New Aircraft for B.O.A.C.'s Western Route", ''Flight'' magazine, January 27, 1949]

{{Boeing airliners}}
{{B-29 family}}
{{Boeing model numbers}}
{{Authority control}}

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