Sixteen passengers and crew on a transatlantic flight were injured as an Air Canada aircraft took a sudden dive in the mistaken belief that it was about to crash into a US military aircraft, according to a report.

The Transportation Safety Board report describes the 46 seconds in which the aircraft dived and lurched back up during an overnight flight from Toronto to Zurich in January 2011.

Those hurt among 103 people on board were not wearing seatbelts, the report said.

The report said flight crews were not following standard procedures for “strategic napping,” which is normally of 40 minutes duration.

Pilots are supposed to have 15 minutes after a nap to awaken properly before taking control, according to safety protocols.

The investigation found that the first officer, who had been asleep for about 75 minutes, was suffering “sleep inertia” magnified by fatigue.

The “confused and disoriented” co-pilot at first mistook the planet Venus for the approaching plane, the report said. When he did spot it, he thought it was coming straight at them. He overrode the auto-pilot by forcefully pressing on the control column, pushing the jet into a dive, according to the report

The captain regained control as the US military plane passed safely and returned the aircraft to its cruising altitude.

“This occurrence underscores the challenge of managing fatigue on the flight deck,” Jon Lee, the investigator in charge, said.

An Air Canada spokesman told the AP news agency that the airline had already taken steps to address 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.