A report on the fatal crash of a forest firefighting plane in B.C. two years ago says an optical illusion and an accidental retardant drop may have combined to cause the accident.
Both pilots of the Conair Aviation tanker were killed when the plane hit some trees, spun out of control and crashed near Lytton in July, 2010.
The report by the Transportation Safety Board says the pilot's depth perception may have been affected by a visual illusion created by the rising terrain He was then unable to avoid the trees.
It also concluded an "unanticipated retardant drop" occurred just as the plane struck the trees.
At the time of the crash the company said it had not had a fatal crash in almost 20 years.