What happened
On a period of low traffic activity in the North Atlantic, a Boeing 747 operated by British Airways, flight BAW92X, was traveling eastbound at flight level 330. Simultaneously, a westbound Lockheed L10 011 operated by Delta Air Lines, flight DAL49, was also cruising at FL330 along the same track.
At approximately 1944 UTC, the two aircraft passed within 1,800 feet of each other, failing to maintain the required 2,000-foot vertical separation. The encounter occurred 225 nautical miles northeast of Gander, Newfoundland. The crew of DAL49 detected the conflict via the Traffic Alert and Collision Avoidance System (TCAS) and chose to expedite their climb to FL350 to avoid the other aircraft. There were no injuries to the 211 passengers and crew on the British Airways flight or the 261 individuals on the Delta Air Lines flight, and no damage was sustained by either aircraft.
The investigation
The investigation focused on the Gander Area Control Centre (ACC) and the failure of multiple controllers to identify the converging flight paths. The Board examined the actions of the oceanic planner, the high-level domestic controller, the trainee, and the instructor.
It was established that the oceanic planner failed to identify the conflict when coordinating the altitude for the British Airways flight. Furthermore, the high-level domestic controller, the trainee, and the instructor all failed to detect the conflict during routine data board scans or during the sector handover briefing. The investigation also noted that the area of the occurrence lacked radar coverage, meaning controllers were reliant on manual flight progress strips.
Findings
- The controllers failed to detect the traffic conflict between DAL49 and BAW92X before the risk of collision became imminent.
- Loss of situational awareness caused by complacency and reduced vigilance during low-traffic periods was a primary contributing factor.
- Controllers relied too heavily on automated systems and failed to follow established manual checklists for data board scans and sector briefings.
- When the conflict was finally identified by the trainee, the clearance provided to DAL49 did not include an instruction to expedite the climb or a traffic advisory regarding the British Airways aircraft.