An Air Canada DC-8 crashes while landing in Toronto, killing 108 people on this day in 1970. The crash was caused by poor landing procedures and inadvertent pilot error. The terrible accident came less than two days after another jet crash had killed more than 100 people in Spain.

The roots of this accident can be found in the working relationship of pilot Peter Hamilton and his co-pilot Donald Rowland. Though they were colleagues who often flew together, they frequently disagreed over the procedure for deploying the wing spoilers at landing. The spoilers are the parts of the wings that assist in braking when they are put in the right position.

Hamilton preferred to “arm the spoilers” or get them ready for deployment, early in the landing process, when the plane was 2,000 feet high, although this was against company policy. Rowland eventually agreed to arm the spoilers before landing, but only when the plane was just above the ground.

On this day, Rowland accidentally deployed the spoilers–rather than merely arming them–as the plane was approaching Toronto’s airport. The premature deployment immediately caused the right wing to plunge to the ground. One engine on the right side fell off and the loss of weight sent the plane back into the air. Hamilton tried to regain control and attempt another landing; as he did, another engine, and then the whole right wing, detached from the plane.

The DC-8 broke into pieces in mid-air near the airport. All 108 people onboard were killed.