Air Canada Flight 621 was operating a scheduled domestic service from Montreal to Toronto on July 5, 1970. The aircraft, a Douglas DC-8-61, was carrying 104 passengers and five crew members when it encountered difficulties while approaching Toronto International Airport. The flight crew executed a go-around after realizing they were improperly configured for landing. Shortly after this decision, the aircraft encountered severe aerodynamic and structural failures, leading to a tragic crash in a rural area of Brampton, Ontario.

During the approach, just moments prior to the tragic ending, the plane's landing gear failed to deploy, forcing the crew to attempt to maintain altitude. Despite their efforts, the plane ultimately crashed into a field, resulting in significant damage and a total loss of life. Witnesses reported seeing the aircraft in distress before it went down, and emergency responders arrived quickly, but unfortunately, there were no survivors.

The investigation into the incident revealed that a combination of factors contributed to the disaster, including mechanical failures and possible crew decision errors. Regulatory changes followed this incident as investigators worked to improve aviation safety standards and procedures. The findings highlighted the need for thorough maintenance and operational protocols concerning aircraft readiness for landing. This crash became a pivotal moment in Canadian aviation history, emphasizing the urgency of enhanced safety measures.