Glider (aircraft)

Lore & Background

Early pre-modern accounts of glider flight are difficult to verify. A 9th-century account describes Abbas Ibn Firnas near Córdoba, Spain, using a feathered wing suit and sustaining minor injuries. A separate 17th-century account reports Hezarfen Ahmet Çelebi gliding across the Bosphorus in Istanbul. The two figures are often conflated in later retellings.

Reader's Guide

Pioneers such as Otto Lilienthal, who made over 2,000 successful flights and first used rising air to prolong flight, advanced aviation. In the inter-war years, recreational gliding flourished in Germany under Rhön-Rossitten, and the Schweizer brothers manufactured sport sailplanes in the United States. Military gliders were developed during World War II for landing troops. Today, gliders are mainly used for sport and recreation, with sailplanes, hang gliders, and paragliders as primary types.

Did You Know?

• Otto Lilienthal was the first to make repeated successful flights, totaling over 2,000, and first used rising air to prolong flight.
• The term 'paraglider' was first used by David Barish in the early 1960s for foot-launched gliders, before NASA adopted it for the Paraglider Research Vehicle.

The Cascade of Human Error

The next day, an avionics technician in Montreal enabled the faulty channel for a self-test, then—distracted by the arrival of the fuel truck—left it enabled after the test failed. When Captain Bob Pearson entered the cockpit, the FQIS was blank. With no electronic readout, he relied on a dripstick measurement, converting centimetres to litres to kilograms. The critical error: he used the fuel density figure from Air Canada's refueler's slip, which expressed density in pounds per litre rather than kilograms per litre. The result was a fuel quantity that appeared sufficient but was actually only 45 percent of what was needed. At Ottawa, the same incorrect conversion was repeated, and no additional fuel was loaded. The navigational computer, which required fuel mass in kilograms, received the wrong number, and the pilots and ground staff all agreed the aircraft had enough fuel.

Seventeen Minutes Without Power

CDT, the cockpit warning system announced a fuel-pressure problem on the left side. The pilots assumed a pump failure and silenced the alarm, knowing the engine could gravity-feed in level flight. Seconds later, the right-side alarm sounded, prompting a diversion to Winnipeg. The left engine died almost immediately, and the crew began preparing for a single-engine approach while attempting a restart. Then came the all-engines-out warning—a sharp bong no one in the cockpit had ever heard before—and the right engine followed. The transponder failed, cutting altitude reporting and forcing controllers back to primary radar. The electronic flight instrument system, powered by the engines, went dark, leaving only battery-backed emergency gauges. Critically, those backup instruments lacked a vertical speed indicator, so the crew could not calculate glide distance. The hydraulic control surfaces, too large for manual muscle power, added another layer of difficulty. The plane came down at Gimli Motorsports Park, a former RCAF base converted to a racetrack, with no serious injuries and only minor damage.

The Aircraft and Its Systems

It was powered by two Pratt & Whitney JT9D-7R4D turbofan engines. When both engines stopped, that system went dead and most screens went blank, leaving the crew with a small set of basic battery-powered emergency flight instruments. Its control surfaces were so large that pilots could not move them with muscle power alone; hydraulic systems were required. The fuel-quantity indicator sensor, a known weak point in 767s with high failure rates, was the system that had malfunctioned, and the only replacement available at the time was itself nonfunctional.

Investigation, Accountability, and Legacy

The board recommended adopting fuelling procedures and safety measures that U.S. and European carriers were already practising, and it called for the immediate conversion of the entire Air Canada fleet from imperial units to SI units, reasoning that a mixed-unit fleet was inherently more dangerous than one operating entirely in imperial or entirely in metric. The incident exposed how a single density figure—expressed in pounds per litre on a refueler's slip, applied to an all-metric aircraft—could produce a 45 percent fuel shortfall that went undetected by pilots, ground crew, and the navigational computer alike. Despite the drama of a 17-minute unpowered glide and a landing on a racetrack, no passengers or ground personnel suffered serious injuries, and the aircraft sustained only minor damage. The plane was repaired and flew for another 25 years. The event earned the aircraft the enduring nickname Gimli Glider, a shorthand that captured both the extraordinary survival and the preventable chain of errors that made it necessary.