On July 23, 1983, Air Canada Flight 143 was en route from Montreal to Edmonton aboard a modern Boeing 767. The aircraft featured an advanced Fuel Quantity Indicator System that happened to be malfunctioning, forcing maintenance crews to manually measure fuel levels using a drip pump stick. The calculation required converting the volume of liquid fuel into mass.
However, Canada was in the middle of transitioning from the Imperial system to the metric system. The refueler used a conversion factor of 1. 77, which was the weight in pounds per liter, instead of the correct metric factor of 0.
857 kilograms per liter. As a result, the aircraft carried less than half the fuel required to complete its journey. Cruising at 41,000 feet over Red Lake, Ontario, the plane's left engine failed, followed shortly by the right engine.
Stripped of all engine power, the massive twinjet lost its primary flight displays and hydraulics. Captain Robert Pearson, an experienced glider pilot, together with First Officer Maurice Quintal, calculated a glide trajectory toward an abandoned Royal Canadian Air Force base in Gimli, Manitoba. Unbeknownst to the crew, the decommissioned runway had been converted into a drag-strip track hosting a crowded family event that day.
Pearson executed a side-slip maneuver to lose altitude without gaining speed, dropping the nose gear via gravity. The nose wheel failed to lock, causing the aircraft to scrape along the guardrail on landing, which generated friction that helped stop the plane mere feet from spectators. All 61 passengers and eight crew members survived without fatal injury, transforming a terrifying mathematical error into one of aviation history's most celebrated emergency landings.