A sleepy passenger jet pilot forced a sudden plane dive after mistaking the planet Venus for a US military plane, injuring 14 people on board the transatlantic flight, according to a newly released report.
The incident occurred during an overnight Air Canada flight from Toronto to Zurich.
Those hurt were not wearing seatbelts, according to the Transportation Safety Board report which describes the 46 seconds in which the plane dived and lurched back up.
The report said the first officer was napping during a scheduled rest period aimed at curbing pilot fatigue when the captain's report on their position woke him up.
In waking, the co-pilot was told by the captain about a US Air Force plane approaching about 300 metres below.
The approach set off cockpit alerts, which the captain mentioned to the first officer.
The "confused and disorientated" first officer mistook Venus for the approaching plane and thought it was coming straight for his plane, said the report.
He overrode the auto-pilot by forcefully pressing on the control column, pushing the jet into a dive.
Fourteen passengers and two flight attendants among the mostly 103 sleeping people aboard slammed into parts of the plane, getting cuts and bruises.
The investigation found the first officer, who had been asleep for about 75 minutes, was suffering "sleep inertia" magnified by fatigue.
The report into the January 2011 incident said flight crews were not following standard procedures for "strategic napping", which is normally 40 minutes in duration.
Pilots are supposed to allow 15 minutes after a nap to awaken properly before taking control, according to safety protocols.
"This occurrence underscores the challenge of managing fatigue on the flight deck," investigator in charge Jon Lee said in a statement.
Air Canada spokesman Peter Fitzpatrick said the company had already taken steps to address the fatigue issues.
Pilots who feel they are too tired to fly have to report it, and a non-punitive system allows them to withdraw from assignments.