What happened
On 16 May 2018, two aircraft flying under instrument flight rules experienced a loss of separation while approaching Montreal/Pierre Elliott Trudeau International Airport. The first aircraft, an Air Transat Airbus A310-304 with registration C-GFAT, was performing flight 485 from Toronto/Lester B. Pearson International Airport. Simultaneously, a privately owned Cessna 421-B, registration C-GADG, was arriving at the Montreal airport from Trois-Rivières Airport.
The Air Transat flight was traveling from the west, positioned to fly north of the airport for an approach to Runway 24R. The Cessna was approaching from the northeast, intending to land on Runway 24L. At 1901:17 Eastern Daylight Time, approximately 18 nautical miles northeast of the airport, the aircraft failed to maintain required separation. At the moment of the loss of separation, the vertical distance between the planes was 200 feet, and the lateral distance was 2.8 nautical miles, violating both the 1000-foot vertical and 3-nautical-mile lateral minimums.
At their closest point, the aircraft were within 500 feet of each other vertically and 1.7 nautical miles laterally. Following interventions by air traffic controllers, the required separation was restored by 1902:22, and both aircraft landed safely without further incident.
The investigation
The investigation examined the circumstances surrounding the separation breach, focusing on the flight paths of both aircraft and the air traffic control environment. The investigation established that the aircraft were operating under instrument flight rules and were on approach to different runways at the time of the event.