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{{short description|1983 aviation accident in Canada}}
{{Use Canadian English|date=June 2020}}
{{Use mdy dates|date=June 2020}}
{{Infobox aircraft occurrence
| occurrence_type = Accident
| name            = Gimli Glider<br>{{nobold|{{small|Air Canada Flight 143}}}}
| image           = Air Canada Flight 143 after emergency landing 2.jpg
| caption         = Photograph of the aircraft after landing at [[Gimli Motorsports Park]]
| date            = {{Start date|1983|07|23|df=y}}
| type            = [[Fuel exhaustion]] due to refuelling error
| site            = Emergency landing at<br />[[Gimli Industrial Park Airport]], Gimli, Manitoba, Canada
| coordinates     = {{Coord|50|37|44|N|97|02|38|W|type:event|display=inline,title}}
| plane1_image    = C-GAUN 604 Boeing 767-233 Air Canada, the "Gimli Glider", Toronto, July 14 1984. (5530418110) (cropped).jpg
| plane1_caption  = C-GAUN, the aircraft involved in the accident, pictured in 1984 after being repaired
| passengers      = 61
| crew            = 8
| aircraft_type   = [[Boeing 767-233]]
| operator        = [[Air Canada]]
| tail_number     = C-GAUN
| IATA            = AC143
| ICAO            = ACA143
| callsign        = AIR CANADA 143
| origin          = [[Montreal-Dorval International Airport]]
| stopover        = [[Ottawa Macdonald–Cartier International Airport|Ottawa International Airport]]
| destination     = [[Edmonton International Airport]]
| occupants       = 69
| injuries        = 10
| fatalities      = 0
| survivors       = 69
}}
[[File:Air Canada Flight 143 after emergency landing.jpg|thumb|C-GAUN from another angle]]
'''Air Canada Flight 143''' was a scheduled domestic [[airline|passenger flight]] between [[Montreal]] and [[Edmonton]] that ran out of fuel on July 23, 1983,<ref>{{Cite web |title=What Happened on July 23, 1983 |url=https://www.onthisday.com/date/1983/july/23 |access-date=2022-12-24 |website=OnThisDay.com |date=July 23, 1983 |language=en}}</ref> midway through the flight. The flight crew successfully [[Gliding flight|glided]] the [[Boeing 767]] from an altitude of {{convert|41000|ft|sigfig=3}} to an [[emergency landing]] at a former [[RCAF Station Gimli|Royal Canadian Air Force base]] in [[Gimli, Manitoba]], which had been converted to a racetrack, [[Gimli Motorsports Park]].<ref name=clojt>{{cite news |url=https://news.google.com/newspapers?id=gtEyAAAAIBAJ&sjid=B-8FAAAAIBAJ&pg=2801%2C1724260 |work=Ottawa Citizen |agency=staff and news services |title=Fuel-starved engines blamed for crash landing of Ottawa jet |date=July 25, 1983 |page=1}}</ref><ref name=jlgdrt>{{cite news |url=https://news.google.com/newspapers?id=hnZkAAAAIBAJ&sjid=7n4NAAAAIBAJ&pg=1522%2C1900057 |work=Calgary Herald |agency=Canadian Press |title=Jetliner glides down on race track |date=July 25, 1983 |page=A1}}</ref> It resulted in no serious injuries to passengers or persons on the ground, and only minor damage to the aircraft. The aircraft was repaired and remained in service until its retirement in 2008. This unusual [[Aviation accidents and incidents|aviation accident]] earned the aircraft the nickname "'''Gimli Glider'''."<ref name="NYT-Witkin">{{cite news |last=Witkin |first=Richard |title=Jet's Fuel Ran Out After Metric Conversion Errors |url=https://www.nytimes.com/1983/07/30/us/jet-s-fuel-ran-out-after-metric-conversion-errors.html |newspaper=[[The New York Times]] |date=July 30, 1983 |access-date=August 21, 2007}}</ref>

The accident was caused by a series of issues, starting with a failed fuel-quantity indicator sensor (FQIS). These had high failure rates in the 767, and the only available replacement was also nonfunctional. The problem was logged, but later, the maintenance crew misunderstood the problem and turned off the backup FQIS. This required the volume of fuel to be manually measured using a [[dripstick]]. The navigational computer required the fuel to be entered in kilograms; however, an incorrect conversion from volume to mass was applied, which led the pilots and ground crew to agree that it was carrying enough fuel for the remaining trip. The aircraft was actually carrying only 45% of its required fuel load.<ref name="NYT-Witkin" /><ref>{{cite web |date=May 22, 2014 |title=Great Miscalculations |url=https://www.bbc.com/news/magazine-27509559 |access-date=January 8, 2016 |website=BBC News}}</ref> The aircraft ran out of fuel halfway to Edmonton, where maintenance staff were waiting to install a working FQIS that they had borrowed from another airline.<ref name="final_report" />

The Board of Inquiry found fault with [[Air Canada]] procedures, training, and manuals. It recommended the adoption of fuelling procedures and other safety measures that U.S. and European airlines were already using. The board also recommended the immediate conversion of all Air Canada aircraft from [[imperial units]] to [[SI system|SI units]], since a mixed fleet was more dangerous than an all-imperial or an all-metric fleet.<ref name="final_report" />

== Aircraft ==
The aircraft involved, manufactured in 1983, was a Boeing 767-233 registered as C-GAUN with [[serial number]] 22520. It was powered by two [[Pratt & Whitney JT9D|Pratt & Whitney JT9D-7R4D]] engines.<ref name="final_report" />

==Accident==
===Background===
On July 22, 1983, Air Canada Boeing 767 {{Airreg|C|GAUN|}} underwent routine checks in Edmonton. The technician found a defective FQIS, so he disabled the defective channel and made an entry in the logbook. The next morning, Captain John Weir and co-pilot Captain Donald Johnson were told about the problem. Since the FQIS was now operating on a single channel, a dripstick reading was taken to obtain a second fuel quantity measurement. Weir converted the dripstick reading from centimetres to litres to kilograms, finding that it agreed with the FQIS. The plane flew to Toronto and then Montreal without incident.<ref name="final_report">{{cite web|author=Lockwood|first=George H.|date=April 1985|title=Final report of the Board of Inquiry investigating the circumstances of an accident involving the Air Canada Boeing 767 aircraft C-GAUN that effected an emergency landing at Gimli, Manitoba, on the 23rd day of July, 1983|url=http://data2.collectionscanada.gc.ca/e/e444/e011083519.pdf|access-date=January 9, 2016|website=Government of Canada}}</ref>

At Montreal, Captain Robert "Bob" Pearson and First Officer Maurice Quintal took over the airplane for Flight 143 to [[Ottawa]] and Edmonton. During the handover, Weir told Pearson that a problem existed with the FQIS, and Pearson decided to take on enough fuel to fly to Edmonton without refuelling in Ottawa. Meanwhile, an avionics technician had entered the cockpit and read the logbook. While waiting for the fuel truck, he enabled the defective channel and performed an FQIS self-test. Distracted by the arrival of the fuel truck, he left the channel enabled after the FQIS failed the test. Pearson entered the cockpit to find the FQIS blank, as he expected.<ref name="final_report" />

The all-metric 767 aircraft, new to the fleet, tracked fuel quantities in kilograms.  After taking a dripstick measurement, Pearson converted the reading from centimetres to litres to kilograms. But he used the density figure for jet fuel from the Air Canada refueler's slip. This figure, used for all other aircraft in the fleet, stated the density in pounds/litre. The correct figure to use was for kilograms/litre, and the  result actually calculated was incorrect.<ref name="ASWEB" /> Since the FQIS was not operational, he entered the miscalculated result into the flight management computer. The airplane flew to Ottawa without accident, where another dripstick measurement was taken, and again, in the same way, converted incorrectly.  Since the aircraft appeared to have enough fuel to reach Edmonton, no fuel was loaded at Ottawa.<ref name="final_report" /><ref name="Deveau">{{cite news |last=Deveau |first=Scott |date=April 14, 2015 |title='Gimli Glider' pilot recalls heroic landing of Air Canada 767 as famed plane put up for sale |url=https://nationalpost.com/news/canada/gimli-glider-pilot-recalls-heroic-landing-of-air-canada-767-as-famed-plane-put-up-for-sale |newspaper=National Post |location=Toronto, Ontario, Canada |access-date=January 9, 2016}}</ref>

===Running out of fuel===
While Flight 143 was flying over [[Red Lake, Ontario]] at {{convert|41000|ft|-2}} shortly after 8 pm [[Central Time Zone|CDT]],<ref name=clojt /> the aircraft's cockpit warning system sounded, indicating a fuel-pressure problem on the aircraft's left side. Assuming that a fuel pump had failed, the pilots turned off the alarm, knowing that the engine could be gravity-fed in level flight.<ref name="WNelson">{{cite web |last=Nelson |first=Wade H. |date=October 1997 |title=The Gimli Glider |url=http://www.wadenelson.com/gimli.html |url-status=live |archive-url=https://archive.today/20121205003036/http://www.wadenelson.com/gimli.html |archive-date=2012-12-05 |access-date=November 9, 2013 |website=WadeNelson.com |publisher=Originally published in [[Soaring (magazine)]]}}</ref> A few seconds later, the fuel pressure alarm also sounded for the right engine. This prompted the pilots to divert to [[Winnipeg James Armstrong Richardson International Airport|Winnipeg]].

The left engine failed within seconds, and the pilots began preparing for a single-engine landing. As they communicated their intentions to controllers in Winnipeg and tried to restart the left engine, the cockpit warning system sounded again with the "all engines out" sound, a sharp "bong" that no one in the cockpit could recall having heard before.<ref name="WNelson" /> The right-side engine stopped seconds later, and the 767 lost all power. Flying with all engines out was never expected to occur, so it had never been covered in training.<ref name=Willams03>{{cite journal |last=Williams |first=Merran |date=July–August 2003 |title=The 156-tonne Gimli Glider |journal=Flight Safety Australia |pages=27 |url=http://www.casa.gov.au/wcmswr/_assets/main/fsa/2003/jul/22-27.pdf| access-date=February 20, 2013 |url-status=dead |archive-url=https://web.archive.org/web/20120326042427/http://casa.gov.au/wcmswr/_assets/main/fsa/2003/jul/22-27.pdf |archive-date=March 26, 2012}}</ref> Adding to both the crew's and the controllers' problems, the plane's [[Transponder (aeronautics)|transponder]] failed, stopping the altitude reporting function and forcing the controllers to revert to [[primary radar]] to track the plane.

The 767 was one of the first airliners to include an [[electronic flight instrument system]], which operated on the electricity generated by the aircraft's jet engines. With both engines stopped, the system went dead, and most screens went blank, leaving only a few basic battery-powered emergency flight instruments. While these provided sufficient information to land the aircraft, the backup instruments did not include a [[vertical speed indicator]] that could be used to determine how far the aircraft could glide.

On the Boeing 767, the [[Flight control surfaces|control surfaces]] are so large that the pilots cannot move them with muscle power alone. Instead, [[Hydraulic drive system|hydraulic systems]] are used to multiply the forces applied by the pilots. Since the engines supply power for the hydraulic systems, in the case of a complete power outage, the aircraft was designed with a [[ram air turbine]] that swings out from a compartment located beneath the bottom of the 767<ref name="WNelson" /> and drives a hydraulic pump to supply power to hydraulic systems.

===Landing at Gimli===
In line with their planned diversion to Winnipeg, the pilots had been descending through {{convert|35000|ft|-2}}<ref name="ASWEB">{{Cite web |last=Ranter |first=Harro |title=Accident description |url=http://aviation-safety.net/database/record.php?id=19830723-0 |url-status=live |archive-url=https://web.archive.org/web/20120128231906/http://aviation-safety.net/database/record.php?id=19830723-0 |archive-date=January 28, 2012 |access-date=July 24, 2008 |website=Aviation Safety Network}}</ref> when the second engine shut down. They had searched their emergency checklist for the section on flying the aircraft with both engines out, only to find that no such section existed.<ref name="WNelson" /> Captain Pearson was an experienced [[Glider aircraft|glider]] pilot, so he was familiar with flying techniques rarely used in commercial flight. Pearson needed to fly the 767 at the optimum [[glide ratio|glide]] speed to have the maximum range and, therefore, the largest choice of possible landing sites. Making his best guess as to this speed for the 767, he flew the aircraft at {{convert|220|kn}}. First Officer Quintal started to calculate whether they could reach Winnipeg. Quintal used the altitude from one of the mechanical backup instruments, while the distance travelled was supplied by the air traffic controllers in Winnipeg, measured by the aircraft's [[radar]] echo observed at Winnipeg. In {{convert|10|nmi}}, the aircraft lost {{convert|5000|ft|m}}, giving a [[glide ratio]] of roughly 12:1. The optimal glide ratio for a Boeing 767-200 is roughly 20:1, achieved at speeds of {{convert|230 - 240|kn}}, and without payload. On dedicated glider planes, glide ratios of up to 70:1 are possible.<ref>{{cite web |date=June 20, 2002 |title=Flugerprobung – Leisting – Leistungsvermessung |trans-title=Flight testing – performance – performance measurement |url=http://www.leichtwerk.de/eta/de/flugerprobung/leistung.html |url-status=dead |archive-url=https://web.archive.org/web/20171113181040/http://www.leichtwerk.de/eta/de/flugerprobung/leistung.html |archive-date=November 13, 2017 |access-date=January 6, 2018 |language=de}}</ref><ref>{{cite web |author=<!-- not stated --> |date=October 18, 1983 |title=The New York Times Q&A - October 18, 1983 issue |url=https://www.nytimes.com/1983/10/18/science/q-a-236305.html|location= |work=The New York Times |access-date=July 8, 2025}}</ref>

At this point, Quintal proposed landing at the former [[RCAF Station Gimli]], a closed air force base where he had once served at a pilot training center for the [[Royal Canadian Air Force]]. Unbeknownst to Quintal or the air traffic controller, a part of the facility had been converted to a race track complex, now known as [[Gimli Motorsports Park]].<ref>{{Cite web |url=http://www.gimlimotorsportspark.com/default.asp |title=Gimli Motorsports Park website |access-date=May 8, 2014 |archive-date=May 8, 2014 |archive-url=https://web.archive.org/web/20140508043049/http://www.gimlimotorsportspark.com/default.asp |url-status=dead}}</ref> It included a road-race course, a [[go-kart]] track, and a [[dragstrip]]. A [[Canadian Automobile Sport Clubs]]-sanctioned sports-car race hosted by the Winnipeg Sports Car Club was underway at the time of the accident. The area around the decommissioned runway was full of cars and campers. Part of the decommissioned runway was being used to stage the race.<ref>{{Cite web|url=http://redriverpca.org/newsletters/2008/PCAprint%20July%20%202008.pdf|archive-url=https://web.archive.org/web/20110727205019/http://redriverpca.org/newsletters/2008/PCAprint%20July%20%202008.pdf|url-status=dead|title=Red River PCA website|archive-date=July 27, 2011}}</ref>

As the aircraft slowed on approach to landing, the reduced power generated by the [[ram air turbine]] rendered the aircraft increasingly difficult to control.<ref name="soaring" /> Without main power, the pilots used a [[Landing gear#Emergency extension systems|gravity drop]] to lower the [[landing gear]] and lock it into place. The main gear locked into position, but the nose wheel did not. The failure of the nose wheel to lock would later prove to be a serendipitous advantage after touchdown for the safety of those on the converted runway.{{Citation needed|date=November 2025}}

As the plane approached the runway, the pilots realized it was coming in too high and fast, increasing the likelihood that the 767 would run off the runway. The lack of hydraulic pressure prevented [[flap (aircraft)|flap]]/[[slat (aircraft)|slat]] extension that would have, under normal conditions, reduced the aircraft's [[stall speed]] and increased the lift coefficient of the wings, to slow the airliner for a safe landing. The pilots briefly considered a 360° turn to reduce speed and altitude, but they decided they did not have enough altitude for the manoeuvre. Pearson decided to execute a [[Slip (aerodynamics)#Forward-slip|forward slip]] to increase drag and reduce altitude. This manoeuvre, performed by "crossing the controls" (applying the rudder in one direction and [[ailerons]] in the other direction), is commonly used in gliders and light aircraft to descend more quickly without increasing forward speed; it is rarely used in large jet airliners outside of rare circumstances like those of this flight.<ref name=soaring /> The forward slip disrupted airflow past the ram air turbine, which decreased the hydraulic power available; the pilots were surprised to find the aircraft slow to respond when straightening after the forward slip.

With both engines completely [[Fuel starvation|starved of fuel]], the plane made hardly any noise during its approach. This gave people on the ground no warning of the impromptu landing and little time to flee. As the gliding plane closed in on the decommissioned runway, the pilots noticed boys were riding bicycles within {{convert|1,000|ft}} of the projected point of impact.<ref name=soaring />{{Failed verification|date=November 2025}}

Two factors helped avert disaster: the failure of the front landing gear to lock into position during the gravity drop, and a guardrail installed along the centre of the repurposed runway to facilitate its use as a drag [[race track]]. Pearson braked hard as soon as the wheels touched down on the runway, skidding and promptly blowing out two of the aircraft's tires. The unlocked nose wheel collapsed and was forced back into its well, causing the aircraft's nose to slam into, bounce off, and then scrape along the ground. This additional friction helped to slow the airplane, and kept it from crashing into the crowds surrounding the runway. Pearson applied extra right brake, which caused the main landing gear to straddle the guardrail. Air Canada Flight 143 came to a final stop on the ground 17 minutes after running out of fuel.<ref name="soaring">{{cite web |author=Nelson |first=Wade H. |date=1997 |title=The Gimli Glider Incident – From an article published in Soaring Magazine |url=http://hawaii.hawaii.edu/math/Courses/Math100/Chapter1/Extra/CanFlt143.htm |access-date=January 8, 2016 |website=hawaii.hawaii.edu/math/Courses/Math100 |publisher=University of Hawai'i |quote=(The dragstrip began in the middle of the runway with the guardrail extending towards 32L's threshold) Pearson applied extra right brake so the main gear would straddle the guardrail. |archive-date=January 1, 2018 |archive-url=https://web.archive.org/web/20180101175134/http://hawaii.hawaii.edu/math/Courses/Math100/Chapter1/Extra/CanFlt143.htm |url-status=dead }}</ref>

No serious injuries occurred among the 61 passengers or the people on the ground. As the aircraft's nose had collapsed onto the ground, its tail was elevated, so some minor injuries occurred when passengers exited the aircraft via the rear [[Evacuation slide|slides]], which were not sufficiently long to accommodate the increased height. Racers and course workers with portable fire extinguishers extinguished a minor fire in the nose area.<ref>{{Cite web |title=The Gimli Glider |url=http://www.damninteresting.com/the-gimli-glider/ |website=www.damninteresting.com |access-date=July 23, 2015}}</ref>

==Investigation==
The Canadian Aviation Safety Board (predecessor of the modern [[Transportation Safety Board of Canada]]) reported that Air Canada management was responsible for "corporate and equipment deficiencies." Their report praised the flight and cabin crews for their "professionalism and skill." It noted that Air Canada "neglected to assign clearly and specifically the responsibility for calculating the fuel load in an abnormal situation."<ref name="final_report" />{{Reference page|page=65}} It further found that the airline had failed to reallocate the task of checking fuel load (which had been the responsibility of the flight engineer on older aircraft flown with a crew of three). The safety board also said that Air Canada needed to keep more spare parts, including replacements for the defective fuel quantity indicator, in its maintenance inventory, and provide better, more thorough training on the metric system to its pilots and fuelling personnel. The final report of the investigation was published in April 1985.<ref name="final_report" />

===Fuel-quantity indication system===
{{More sources|section|date=October 2024}}
The amount of fuel in the tanks of a Boeing 767 is computed by the FQIS and displayed in the cockpit. The FQIS on the aircraft was a dual-processor channel, each independently calculating the fuel load and cross-checking with the other. In the event of one failing, the other could still operate alone, but in that case, the indicated quantity was required to be cross-checked against a [[floatstick]] measurement before departure. If both channels fail, no fuel display was seen in the cockpit, and the aircraft would be considered unserviceable and not authorized to fly.

Because inconsistencies had been found with the FQIS in other 767s, Boeing issued a service bulletin for the routine checking of this system. An engineer in Edmonton duly did so when the aircraft arrived from Toronto following a trouble-free flight the day before the accident. While conducting this check, the FQIS failed, and the cockpit fuel gauges went blank. The engineer had encountered the same problem earlier in the month when this same aircraft had arrived from Toronto with an FQIS fault. He found then that disabling the second channel by pulling the [[circuit breaker]] in the cockpit restored the fuel gauges to working order, albeit with only the single FQIS channel operative. Without any spares, he repeated this temporary fix by pulling and tagging the circuit breaker.

A record of all actions and findings was made in the maintenance log, including the entry: "SERVICE CHK – FOUND FUEL QTY IND BLANK – FUEL QTY #2 C/B PULLED & TAGGED...".<ref>{{cite book |last=Stewart |first=Stanley |title=Emergency, Crisis on the Flightdeck |year=1992 |publisher=Airlife Publishing Ltd |isbn=978-1-85310-348-3 |page=123}}</ref> This reports that the fuel gauges were blank and that the second FQIS channel was disabled, but it does not make clear that the latter fixed the former.

The aircraft flew from Edmonton to Montreal on the day of the accident. Before departure, the engineer informed the pilot of the problem and confirmed that the tanks must be verified with a floatstick. In a misunderstanding, the pilot believed the aircraft had been flown with the fault from Toronto the previous afternoon. The flight to Montreal proceeded uneventfully, with fuel gauges operating correctly on the single channel.

On arrival in Montreal, a new crew boarded for the return flight to Edmonton. The outgoing pilot informed Captain Pearson and First Officer Quintal of the problem with the FQIS and passed along his mistaken belief that the aircraft had flown the previous day with this problem. In a further misunderstanding, Captain Pearson believed he was also being told that the FQIS had been completely unserviceable since then.

While the aircraft was being prepared to return to Edmonton, a maintenance worker decided to investigate the problem with the faulty FQIS. To test the system, he re-enabled the second channel, at which point the fuel gauges in the cockpit went blank. However, before he could disable the second channel again, he was called away to perform a floatstick measurement of fuel remaining in the tanks, leaving the circuit breaker tagged (which masked the fact that it was no longer pulled). The FQIS was now completely unserviceable, and the fuel gauges were blank.

On entering the cockpit, Captain Pearson saw what he was expecting to see—blank fuel gauges and a tagged circuit breaker. Pearson consulted the [[master minimum equipment list]] (MMEL), which indicated that the aircraft was not legal to fly with blank fuel gauges. Still, due to a misunderstanding, Pearson believed it was safe to fly if the amount of fuel was confirmed with measuring sticks.<ref name="ASN">{{cite web |url=http://aviation-safety.net/database/record.php?id=19830723-0 |title=Accident Boeing 767-233 C-GAUN, Saturday 23 July 1983 |author=<!--Staff writer(s); no by-line.--> |date=2016 |website=[[Aviation Safety Network]] |access-date=November 3, 2024}}</ref>

The 767 was still a very new aircraft, having flown its [[maiden flight]] in September 1981. C-GAUN was the 47th Boeing 767 off the production line and had been delivered to Air Canada fewer than four months prior to this flight. In that time, 55 changes had been made to the MMEL, and some pages were blank pending development of procedures.

Because of this unreliability, maintenance personnel authorizing flights had become standard practice. To add to his misconceptions about the aircraft's flying condition since the previous day, reinforced by what he saw in the cockpit, Pearson now had a signed-off maintenance log, which had become customarily preferred over the MMEL.

=== Miscalculation during fuelling ===
In older aircraft with a three-person crew, the [[flight engineer]] kept a fuel log and supervised the fuelling. The Boeing 767 belonged to a new generation of aircraft that flew with only a pilot and co-pilot, but Air Canada had not clearly assigned responsibility for supervising the fuelling.<ref name="final_report" />{{Reference page|page=|pages=64–65}} On the day of the accident, two technicians and two pilots worked on the calculation in Montreal. One technician stopped after he found that he was not making any progress. Another technician was using a piece of paper in his pocket, and he stopped when he ran out of space. First Officer Quintal did the calculation by hand, and Captain Pearson checked the arithmetic with his [[Jeppesen]] [[slide rule]].<ref name="final_report" />{{Reference page|page=|pages=40–41}}

Since the FQIS was not working, Captain Pearson decided to take on enough fuel to reach Edmonton without refuelling at Ottawa.<ref name="final_report" />{{Reference page|page=26}} The flight plan showed that {{convert|22300|kg}} of fuel were required for the flight from Montreal to Ottawa to Edmonton. A dripstick check found that {{convert|7682|L}} of fuel was already in the tanks. To calculate how much fuel the airplane had to take on, he needed to convert the 7,682{{nbs}}litres of fuel already in the tanks to their equivalent mass in kilograms, subtract that figure from the 22,300&nbsp;kg total fuel that would be needed, and convert that result back into its equivalent volume.<ref name="final_report" />{{Reference page|page=41}} The density in metric units was 0.803&nbsp;kg/L, so the correct calculation would have been:

:7,682 L × 0.803 kg/L = 6,169 kg = mass of fuel already on board
:22,300 kg − 6,169 kg = 16,131 kg = mass of additional fuel required, or
:16,131 kg ÷ (0.803 kg/L) = 20,088 L = volume of additional fuel required

At the time of the accident, Canada's aviation sector was converting from imperial to metric units. As part of this process, the new 767s acquired by Air Canada were the first to be calibrated for metric units.<ref name="final_report" />{{Reference page|page=|pages=63–64}} The fueler reported that the density of jet fuel at the time was 1.77, which was in lb/L, since other Air Canada aircraft used lb. Pearson and Quintal both used the density of jet fuel in lb/L without converting to kg/L:<ref name="final_report" />{{Reference page|page=|pages=40–41}}

:7,682 L × 1.77 lb/L = 13,597 lb = misinterpreted as kilograms of fuel already on board
:22,300 kg − 13,597 kg = 8,703 kg = incorrect mass of additional fuel required
:8,703 kg ÷ (1.77 lb/L) = 4,917 L·kg/lb = misinterpreted as litres of additional fuel required

Instead of taking on the {{convert|20,088|L}} of additional fuel that they required, they took on only {{convert|4,917|L}}. The use of the incorrect conversion factor led to a total fuel load of only {{convert|22300|lb|kg|abbr=on}} rather than the {{convert|49170|lb|kg|abbr=on}} that were needed. This was less than half of the amount required to reach their destination.<ref>{{cite web |url=http://code7700.com/mishap_air_canada_143.html |title=Air Canada 143 – Accident Case Study |website=www.code7700.com |date=June 7, 2014 |access-date=September 15, 2016 |archive-date=October 8, 2016 |archive-url=https://web.archive.org/web/20161008031256/http://code7700.com/mishap_air_canada_143.html |url-status=dead}} (the source contains two typos regarding the weight of fuel already on board: ''6669'' and ''66169'', instead of the correct value of ''6169'')</ref>

The flight management computer (FMC) measures fuel consumption, allowing the crew to keep track of fuel burned as the flight progresses. It is normally updated automatically by the FQIS, but the fuel quantity can also be entered manually. Because the FMC would reset during the stopover in Ottawa, the captain had the fuel tanks measured again with the [[dripstick]]. With {{convert|11,430|litre}} of fuel in the tanks, the fueler gave a density of 1.78. Repeating the same error, Captain Pearson determined that he had {{convert|20,400|kg|abbr=on}} of fuel and entered this number into the FMC. However, he actually had just {{convert|20400|lb|kg|-1|order=flip|abbr=on}} of fuel.<ref name="final_report" />{{Reference page|page=|pages=42–43}}

The previous flight from Edmonton to Montreal had avoided the error. The fueler at Edmonton knew the density of jet fuel in kg/L, and he calculated the correct number of litres to pump into the tanks. He testified that it was a "regular practice of his" to do such calculations. When fuelling was complete, Captains Weir and Johnson checked the figures. The captain knew "from previous experience" the density of jet fuel in kg/L. He also had a working FQIS, which agreed with his calculations.<ref name="final_report" />{{Reference page|page=|pages=43–44}}

==Aftermath==
Following Air Canada's internal investigation, Captain Pearson was demoted for six months, and First Officer Quintal was suspended for two weeks for allowing the accident to happen. Three maintenance workers were also suspended.<ref name="PilotDemoted">{{cite news |url=http://www.cbc.ca/news/canada/manitoba/gimli-glider-recalled-at-trial-of-pilot-in-crash-1.646493 |title='Gimli glider' recalled at trial of pilot in crash |date=April 26, 2007 |publisher=CBC |access-date=November 9, 2013}}</ref> Following a successful appeal against their suspensions, Pearson and Quintal were assigned as crew members aboard another Air Canada flight. In 1985, Pearson and Quintal were awarded the first ever [[Fédération Aéronautique Internationale]] Diploma for Outstanding Airmanship.<ref>{{cite web |url=http://www.fai.org/awards/award.asp?id=26 |title=FAI Diploma for Outstanding Airmanship |access-date=June 5, 2007 |url-status=dead |archive-url=https://web.archive.org/web/20071011105839/http://www.fai.org/awards/award.asp?id=26 |archive-date=October 11, 2007}}</ref> Several attempts by other crews who were given the same circumstances in a simulator at Vancouver resulted in crashes.<ref>TV program ''Air Crash Investigation'' National Geographic Channel</ref> Quintal was promoted to captain in 1989.<ref name="FinalGimli">{{cite news |url=https://www.theglobeandmail.com/news/national/storied-gimli-glider-on-final-approach/article666567/ |title=Storied 'Gimli Glider' on final approach |last=Jang |first=Brent |newspaper=[[The Globe and Mail]] |date=March 13, 2009 |access-date=November 9, 2013}}.</ref> Pearson remained with Air Canada for ten years and then moved to flying for [[Asiana Airlines]]; he retired in 1995.<ref name="Deveau" />  Maurice Quintal died at the age of 68 on September&nbsp;24, 2015, in [[Saint-Donat, Lanaudière, Quebec|Saint-Donat, Quebec]].<ref>{{cite web |url=https://www.afterlife.co/ca/obituary-saint-donat-maurice-quintal-425919 |archive-url=https://web.archive.org/web/20160825214959/https://www.afterlife.co/ca/obituary-saint-donat-maurice-quintal-425919 |url-status=dead |archive-date=August 25, 2016 |title=Obituary of Maurice Quintal |date=October 15, 2015 |access-date=June 29, 2016}}</ref>

The aircraft was temporarily repaired at Gimli and flew out two days later to be fully repaired at a maintenance base in Winnipeg. The aircraft was returned to service with Air Canada after the full repair.

The 1995 television movie ''[[Falling from the Sky: Flight 174]]'' is loosely based on this event.

The [[Discovery Channel Canada]] / [[National Geographic Society|National Geographic]] TV series ''[[Mayday (Canadian TV series)|Mayday]]'' covered the accident in a 2008 episode titled "Gimli Glider". The episode featured interviews with survivors, including Pearson and Quintal, and a dramatic flight recreation.<ref name="Mayday Gimli Glider">{{Cite episode|title=Gimli Glider|series=[[Mayday (Canadian TV series)|Mayday]]|network=[[Discovery Channel Canada]] / [[National Geographic Channel]]|season=5|year=2008}}</ref>

==Retirement==
[[File:Aca-767-C-GAUN-604-080201-01-8.jpg|right|thumb|C-GAUN parked at [[Mojave Airport & Spaceport]] in February 2008 (C-GAUN's Air Canada livery was subsequently removed.)]]
After almost 25 years of service, C-GAUN flew its last revenue flight on January&nbsp;1, 2008. The Gimli Glider then began its final voyage on January&nbsp;24, 2008, as AC7067, from Montreal Trudeau to [[Tucson International Airport]] and final flight to retirement at California's [[Mojave Air and Space Port|Mojave Airport]]. The flight was captained by Jean-Marc Bélanger, a former head of the [[Air Canada Pilots Association]]; captains Robert Pearson and Maurice Quintal were also on board, as were three of the six flight attendants from Flight 143.<ref name="WNelson" /><ref name="FinalGimli" />

That summer, on July 23, 2008, the 25th anniversary of the accident, pilots Pearson and Quintal were celebrated in a parade in Gimli, and a mural was dedicated to commemorate the landing.<ref>{{cite news |url=http://www.cbc.ca/news/canada/manitoba/hero-pilot-is-guest-for-gimli-glider-25th-anniversary-1.766236 |title=Hero pilot is guest for Gimli Glider 25th anniversary |publisher=CBC News |date=July 23, 2008|access-date=November 9, 2013}}</ref>

In April 2013, the Gimli Glider was offered for sale at auction, by a company called Collectable Cars,<ref name="Deveau" /> with an estimated price of {{CAD|2.75–3 million}}.<ref>{{cite web |author= |date=February 22, 2013 |title=Boeing 767 known as Gimli Glider up for auction |url=https://www.thestar.com/news/canada/2013/02/22/boeing_767_known_as_gimli_glider_up_for_auction.html |access-date=June 26, 2013 |work=Winnipeg Free Press |via=TheStar.com}}</ref> However, bidding only reached {{CAD|425,000}} and the lot was unsold.<ref>{{cite web |url=https://www.cbc.ca/news/canada/manitoba/gimli-glider-not-sold-at-ontario-auction-1.1394807 |title='Gimli Glider' not sold at Ontario auction |work=CBC News |date=April 14, 2013 |access-date=June 26, 2013}}</ref>

According to a website dedicated to saving the aircraft, the Gimli Glider was scrapped in early 2014. Parts of the metal fuselage skin were made into 10,000 sequentially numbered luggage tags, and {{as of|2015|lc=y}}, were offered for sale by a California company, MotoArt, under the product name "PLANETAGS".<ref name=iltoday20151216>{{cite news |last=Debooy |first=Erin |date=December 16, 2015 |title=Boeing 767 that landed near Gimli being repurposed into luggage tags |url=http://www.interlaketoday.ca/2015/12/16/boeing-767-that-landed-near-gimli-being-repurposed-into-luggage-tags |newspaper=Interlake Spectator, Postmedia |location=Gimli, Manitoba |access-date=January 9, 2016 |archive-url=https://web.archive.org/web/20160127071834/http://www.interlaketoday.ca/2015/12/16/boeing-767-that-landed-near-gimli-being-repurposed-into-luggage-tags |archive-date=January 27, 2016 |url-status=dead}}</ref>

In June 2017, a permanent museum exhibit of the event opened in Gimli. The exhibit includes a cockpit mock-up flight simulator, and {{as of|July 2017|lc=y}}, sold event memorabilia.<ref name="wfreepress20170721">{{cite news |author=Rollason |first=Kevin |date=July 21, 2017 |title=Gimli commemorates historic airline touchdown with new exhibit |url=https://www.winnipegfreepress.com/local/smooth-landing-for-new-exhibit-435945543.html |access-date=February 25, 2018 |newspaper=Winnipeg Free Press}}</ref>

On June 27, 2025, The Gimli Glider Exhibit museum displayed the recently recovered and transported cockpit of C-GAUN in a ceremony reuniting it with Captain Robert "Bob" Pearson.<ref>{{cite news |author=Joseph Bernacki |publisher=CTV News |date=June 27, 2025 |title= 'It's a piece of aviation history': Gimli Glider cockpit makes return trip to Manitoba |url=https://www.ctvnews.ca/winnipeg/article/its-a-piece-of-aviation-history-gimli-glider-cockpit-makes-return-trip-to-manitoba/ |access-date=June 28, 2025}}</ref>

==See also==
* [[List of airline flights that required gliding]]
* [[List of accidents and incidents involving commercial aircraft]]
* [[Cornfield Bomber]]

==References==
{{Reflist|30em}}

==Further reading==
{{refbegin}}
* ''Emergency, Crisis on the Flight Deck'', Stanley Stewart, Airlife Publishing Ltd., 1992, {{ISBN|1-85310-348-9}}
* ''Freefall: From 41,000 feet to zero – a true story'', William and Marilyn Hoffer, [[Simon & Schuster]], 1989 {{ISBN|978-0-671-69689-4}}
* ''Engineering Disasters – Lessons to be Learned'', Don Lawson, ASME Press, 2005, {{ISBN|0-7918-0230-2}}, pp. 221–29 deal specifically with Gimli Glider.
{{refend}}

==External links==
* [http://www.gimliglider.org The Gimli Glider Exhibit website]
* [http://www.damninteresting.com/the-gimli-glider Damn Interesting: The Gimli Glider]
* [http://www.cbc.ca/archives/categories/science-technology/measurement/for-good-measure-canada-converts-to-metric/gimli-glider-lands-without-fuel.html CBC Digital Archives: 'Gimli Glider' lands without fuel]
* [http://www.jetphotos.net/viewphoto.php?id=251010 Photo of C-GAUN after the landing]
* [http://www.airliners.net/photo/Boeing-767-233/1481973/L/ Picture of C-GAUN in storage (airliners.net)]
* {{YouTube|id=2MHy6yy3Z00|title=Video of retirement fly-by}}

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