The Gimli Glider: When a Boeing 767 Ran Out of Fuel Mid-Air

How the Fuel Was Calculated Wrong

The Boeing 767 was the first Canadian aircraft to require fuel to be measured in kilograms rather than pounds. This was part of Canada's transition to metric, which was underway in 1983. The 767's fuel quantity gauges were malfunctioning — a known issue that had not been resolved — so the fuel load had to be calculated manually.

The calculation required knowing the fuel density to convert volume (liters) to mass. Fuel density in aviation is the conversion factor between liters and the weight of fuel. The correct factor for jet fuel is approximately 0.803 kg/L. The ground crew used 1.77 — which is the conversion factor for pounds per liter, not kilograms per liter.

1.77 lbs/L is approximately correct in the pounds system. 0.803 kg/L is correct in the metric system. By using the pounds-per-liter factor in a calculation that expected kilograms, the crew calculated the fuel mass as roughly 2.2 times larger than it actually was. The aircraft departed with less than half the fuel required for the flight from Montreal to Edmonton.

The Sequence of Events

The aircraft flew normally from Montreal to Ottawa, then Ottawa to Winnipeg. At Winnipeg, maintenance was done on the fuel gauges — the underlying fault was not corrected. The crew accepted a manual fuel calculation and departed for Edmonton.

At 41,000 feet over Red Lake, Ontario, the left engine flamed out. Minutes later, the right engine followed. The 767 became a glider with no hydraulic power (which runs off the engines), only a ram air turbine deploying from the fuselage to provide minimal electrical and hydraulic power for controls.

Captain Robert Pearson, an experienced glider pilot in his spare time, executed a textbook dead-stick approach. He aimed for the closed airstrip at Gimli, Manitoba — the closest suitable landing area. The aircraft was moving too fast with no engine braking and no thrust reversers. Pearson executed a maneuver called a sideslip to bleed speed, which is extremely rare in jet aircraft.

The Landing and the Outcome

The Gimli airstrip was not just abandoned — it was hosting a drag racing event. The drag racers had parked on the runway. As the 767 approached with no power and no radio contact with Gimli's unmanned tower, spectators scattered. The aircraft touched down hard, the nose gear collapsed, and the aircraft slid to a stop. There were minor injuries from the evacuation — twisted ankles, a few burns from the emergency slides — but no fatalities.

The investigation found multiple layers of failure. The fuel gauges had a known defect. The dispatch paperwork passed through multiple hands without anyone catching the unit error. The minimum equipment list — which governs what faults are acceptable for flight — was incorrectly interpreted to allow flight with the gauge fault. The unit error itself was a product of an undertrained crew during Canada's metric transition.

Captain Pearson and First Officer Maurice Quintal were initially suspended by Air Canada, then had their penalties reduced after the investigation clarified the systemic nature of the failures. Both returned to flying.

What Changed After Gimli

The Gimli incident accelerated changes to Canadian aviation fuel handling procedures. Cross-checks between manual fuel calculations and fuel-uplifted records were made mandatory. The specific calculation sheet that led to the error was redesigned to make the unit (kg or lbs) explicit in every field.

The 767 "Gimli Glider" aircraft was repaired and returned to service. It flew for Air Canada until 2008 and was then operated by charter carriers until 2013 before being scrapped. Its registration, C-GAUN, became one of the most recognized in Canadian aviation history.

Conclusion

The Gimli Glider ran out of fuel because a density conversion factor in pounds (1.77 lbs/L) was used in a calculation that expected kilograms (0.803 kg/L) — overstating the fuel load by a factor of 2.2. The aircraft glided 100 km and landed safely on a drag racing track thanks to exceptional piloting. The incident became a landmark case in aviation safety for its illustration of how unit errors in critical calculations cascade into catastrophic outcomes.