What happened
At approximately 1114 mountain daylight time, two large commercial aircraft were operating on converging tracks at flight level 340 within the controlled Class A airspace of the North High specialty. The first aircraft, a Boeing 747-400 operated by Lufthansa (DLH492), was traveling from Frankfurt, Germany, to Vancouver, British Columbia. The second aircraft, an Airbus A340-500 operated by Air Canada (AC015), was en route from Toronto, Ontario, to Hong Kong.
While the aircraft were intended to maintain a minimum separation of 15 minutes for crossing tracks at the same altitude, the actual spacing between the two flights was only 10 minutes. The loss of separation was discovered by an air traffic controller after a position report indicated a time discrepancy, revealing that the flight plan for the Lufthansa aircraft had been programmed with incorrect fixes and an incorrect fix reference number (FRN).
The investigation
The investigation focused on the accuracy of the flight plan setup and the operational environment within the Edmonton Area Control Centre. Investigators examined the Northern Airspace Display System (NSiT) used by controllers to predict conflicts. It was determined that the NSiT was programmed with incorrect data for the DLH492 route, which caused the system to calculate a separation distance greater than the actual distance, thereby failing to trigger a conflict alert.
The investigation also scrutinized the staffing levels and work schedules of the air traffic controllers. At the time, the Edmonton ACC was operating at approximately 83 per cent of its required staffing. Investigators analyzed the shift rotations and rest periods of the three controllers involved, using the Fatigue Avoidance Scheduling Tool (FAST) to assess the impact of their schedules on performance.
Findings
- Controller fatigue was a primary contributing factor, as the controllers were likely experiencing impaired vigilance and motivation due to scheduling practices that provided insufficient recovery time.
- A flight plan error occurred when an incorrect FRN and incorrect fixes were entered into the system, which the NSiT could not detect because it lacks automated route conformance checking.
- The lack of a formal crosscheck procedure for verifying data accuracy during flight plan activation allowed the incorrect information to go undetected by subsequent controllers.
- Distractions, including an unusual call sign suffix ("M") and specific requests for altitude information, hindered the controllers' ability to notice discrepancies in position reports.
- Inconsistent formatting between flight progress strips and verbal position reports made it more difficult for controllers to identify errors in the aircraft's track.