The Transportation Safety Board says it doesn’t know what caused a plane operated by Mount Royal University’s flight school to lose control and crash northwest of Calgary.
The crash a year ago killed pilot Jeffrey Bird and co-pilot Reynold Johnson, who were both instructors with the program.
A safety board investigation report says that for unknown reasons the aircraft started spinning during an exercise about a half hour after it took off from the Calgary Springbank Airport.
Bird and Johnson managed to get the plane out of the spin, but by then there was not enough altitude to recover from the ensuing dive.
READ MORE: Flight instructors killed in plane crash near Calgary were experienced pilots: Mount Royal University president
The board says Mount Royal took a number of safety actions after the crash, acquired different aircraft for multi-engine training and revised operating procedures.
It also clarified roles for when two instructors are on staff training flights together.