A groggy Air Canada pilot who mistakenly believed his jet was about to smash into another plane forced a sudden dive that caused 16 injuries among passengers and crew on a transatlantic flight, said a report released Monday.
The Transportation Safety Board report notes that those hurt aboard the Boeing 767 had failed to comply with lit seatbelt signs.
"This occurrence underscores the challenge of managing fatigue on the flight deck," Jon Lee, the investigator in charge, said in a statement.
"It also shows that in-flight passenger injuries can be prevented by wearing seatbelts at all times while seated."
The terrifying 46 seconds, in which the plane dove 120 metres then lurched 240 metres back upward, occurred in January, 2011 aboard an overnight Air Canada flight from Toronto to Zurich.
The first officer was napping during a controlled rest period aimed at combating pilot fatigue when he was awakened by the captain's report of their flight position.
At the same time, a U.S. air force Boeing C-17 was coming from the opposite direction about 300 metres below them. The approach sparked cockpit alerts, which the captain mentioned to his groggy flight officer.
The "confused and disoriented" co-pilot first mistook the planet Venus for the approaching aircraft. When he did spot the oncoming plane, he thought it was descending straight at them.
To avoid what he thought was an imminent collision, the first officer overrode the auto-pilot by forcefully pressing on the control column, pushing the passenger jet into a dive.
The captain was able to regain control as the C-17 passed safely below them, and returned the plane to its cruising altitude.
In all, 14 passengers and two flight attendants among the mostly 103 sleeping people aboard suffered bruises and cuts from slamming into aircraft fixtures. Seven were treated in hospital on arrival in Zurich three hours later.
None of the injured was buckled up even though seatbelt signs had been on for 40 minutes because of concerns over turbulence.
"Some passengers may not be aware of the inherent risks in not wearing a seatbelt at all times when seated," the report notes.
The investigation found that the first officer, who had been asleep for about 75 minutes, was suffering "sleep inertia" magnified by fatigue.
The report notes flight crews did not fully understand the risks associated with fatigue, nor were they following standard procedures for "strategic napping," which is normally of 40 minutes duration.
Pilots are also supposed to have 15 minutes after a nap to awaken properly before taking control, according to safety protocols.
Capt. Paul Strachan, president of the Air Canada Pilots Association, said the incident shows Ottawa needs to mandate a third pilot for taxing eastbound transatlantic flights instead of the "hokey" in-flight rest periods.
An extra pilot would allow a colleague to leave the cockpit for proper rest, rather than making one of the two co-pilots take a 40-minute nap.
"What if something happens to the other pilot during that 40 minutes?" Capt. Strachan said.
"The only reason there isn't a third pilot on that flight is so they don't have to pay a third pilot."
No U.S. carriers would fly that route with fewer than three pilots, and even India's rules are stricter, he said.
"Canada's regulations are stark in their insensitivity to the science of fatigue."
Air Canada spokesman Peter Fitzpatrick said it is not possible to generalize when it comes to a mandated third pilot because "there are numerous considerations when assessing the need for augmentation."
However, he said the company had already taken steps to address the fatigue issues and would study the final report to see if further measures might be needed.
Among other things, the carrier is developing a better tracking system for specialized fatigue reports. Also, pilots who feel they are too tired to fly have to report that fact, and a non-punitive system is in place that allows them to withdraw from assignments, Air Canada said.