The Transportation Safety Board says it was likely a buildup of ice that caused a fatal plane crash west of Calgary.
Two people were in the four-seater aircraft when it went down along the Trans-Canada Highway near the Springbank Airport on April 22.
The pilot was killed and a passenger was taken to hospital with life-threatening injuries.
The pilot, identified as Michael James Wilton, was the president of FlightSimple, an aircraft sales company.
The safety board’s final report says the plane was not equipped or certified for flying in icy conditions, but it did have an electric de-icing system on the propeller.
It says the plane’s engine was operating normally, but even a small amount of ice would have affected the flight.
Photos taken by the RCMP after the crash show ice up to 2.5 centimetres thick was on parts of the plane, including the leading edge of its left wing.