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Associated links (A19O0117)

Misinterpretation of air traffic control communication identified as a factor in August 2019 runway incursion at Toronto/Lester B. Pearson International Airport

Richmond Hill, Ontario, 15 January 2021 — The Transportation Safety Board of Canada (TSB) today released its investigation report (A19O0117) into the August 2019 runway incursion between two aircraft at the Toronto/Lester B. Pearson International Airport, Ontario. There were no injuries.

On 9 August 2019 at 1240 local time, an Air Canada Boeing 777-300 landed on Runway 33L. Three minutes later, at 1243 local time, an Air Georgian Bombardier CRJ 200 was instructed to line up on parallel Runway 33R. In accordance with air traffic control (ATC) instructions, the Boeing 777 was crossing Runway 33R. Simultaneously, the flight crew of the CRJ 200 began its take-off roll on the same runway without a take-off clearance from ATC. When the CRJ 200 flight crew saw the Boeing 777 over the crest of the runway, they rejected the takeoff and exited via a taxiway.

The investigation found that while completing the pre-departure checks, the flight crew of the CRJ 200 was informed of a change in departure instructions. The first officer received and read back the line-up instruction with the departure amendment, but misinterpreted that ATC communication as a clearance for takeoff.

It was determined that the number of pre-departure tasks the flight crew was required to complete within a short amount of time increased their workload, and that the workload was further increased by the additional tasks brought by the change in instructions. Thus, it was found that the increased workload, the expectation to receive a take-off clearance without delay, and the misinterpretation of the line-up instructions led the CRJ 200 flight crew to initiate take-off roll without a take-off clearance. Also, because of the grade profile of Runway 33R, the fuselage of the Boeing 777 would not have been visible to the CRJ 200 flight crew at the start of the take-off roll, therefore they had no visual indication that it was unsafe to begin the takeoff.

Both flight crew members worked an early morning shift after working an evening shift, known as a backward-rotating shift schedule. Although the investigation did not determine that fatigue affected the performance of the flight crew in this occurrence, backward-rotating shift schedules cause circadian rhythm desynchronization, which increases the risk of fatigue in crew members who do not receive sufficient time off to adapt their sleep-wake pattern when working these schedules. Furthermore, if airlines do not inform crew members of the risk of fatigue due to the direction of shift schedule rotation, there is an increased risk that crew members will operate an aircraft while fatigued.

Following the occurrence, NAV CANADA issued a directive reminding air traffic controllers to cancel the take-off clearance or issue an instruction to abort takeoff when runway incursion monitoring and conflict alert system stage 2 alerts are activated by a departing aircraft.

Air Georgian Limited conducted an internal safety investigation as per the company's safety management system. It amended its standard operating procedures to mandate an ATC query if one of the two crew members was unaware of the content of an ATC clearance or instruction.

See the investigation page for more information.


The TSB is an independent agency that investigates air, marine, pipeline, and rail transportation occurrences. Its sole aim is the advancement of transportation safety. It is not the function of the Board to assign fault or determine civil or criminal liability.

For more information, contact:
Transportation Safety Board of Canada
Media Relations
Telephone: 819-994-8053
Email: media@tsb.gc.ca