A tragedy was narrowly averted on May 16, 2018, at the Montreal-Trudeau Airport, when an Air Transat Airbus A310 and a Cessna 421 twin-engine aircraft were approaching to land,  a report from the Office of Safety and Security of Canada. Transport (BST) made public on Wednesday.

“There was a loss of separation between the two aircraft when they were about 18 nautical miles (33.33 km) northeast of the airport,” says the TSB report. At the closest point, the two aircraft were within 500 feet vertically and 1.7 nautical miles (3.15 km) sideways from each other. Normally, the minimum required vertical separation between aircraft is 1000 feet and the minimum lateral separation is 3 nautical miles (5.56 km). ”

This incident was allegedly caused by a lack of air traffic controllers that night.

According to the TSB, seven air traffic controllers and one supervisor should have been posted that night, but due to absences and discomfort, there were only three controllers and one supervisor on duty.