About five minutes after takeoff in poor weather, the jet crashed about 32 km (20 mi) north of Montreal, near Ste-Thérèse-de-Blainville, Quebec, Canada, killing all 111 passengers and seven crew members.

[1][4] The aircraft involved was a Douglas DC-8 54CF series, powered by four Pratt & Whitney JT3D engines and delivered new to Trans-Canada Air Lines nine months prior to the accident.

[9] Although parts of the airplane were scattered over a wide area ahead of and separate from the crater, the commission of inquiry found that the aircraft was structurally intact when it struck the ground.

Although the official report released in 1965 could not determine the cause of the accident, it pointed to problems in the jet's pitch trim system (the device that maintains a set nose-up or nose-down attitude) as a possibility, as a pitch trim problem caused the similar crash of Eastern Air Lines Flight 304, another DC-8, three months after the crash of Flight 831.

"[8] The plane's flight crew included 47-year-old captain John D. "Jack" Snider of Toronto, a World War II bomber pilot, 35-year-old first officer Harold J.

[8] Traffic congestion on Montreal's main expressway, which extended all the way into the downtown core, caused eight people to miss the flight but also impeded emergency vehicles from reaching the crash site.

In November 1965, the CBC broadcast the hour-long documentary[13] which was watched by more than two million Canadians, but many victims' families avoided it, not wanting to revisit the tragedy.