Canadian controllers intervened to stop a Jazz Bombardier Q400 from departing Thunder Bay airport without clearance, as a second aircraft prepared to land on an intersecting runway.
The Jazz aircraft had been cleared to position and hold on runway 25 ahead of a flight to Toronto on 9 March, according to the Transportation Safety Board.
But it states that tower controllers saw the turboprop initiating its take-off roll "without a clearance".
The second aircraft, a Wasaya Airways Beech 1900D, had already been cleared to land on runway 12, which intersects the far end of runway 25.
In a bulletin on the incident the safety board says controllers instructed the Q400 to stop, and to exit the runway and wait on taxiway B, owing to an inbound Pilatus PC-12 conducting a medevac flight to runway 25.