The Transportation Safety Board (TSB) of Canada said this week that multiple factors were responsible for the altitude deviation of one of its Boeing 767s in January 2011. On a flight between Toronto and Zurich, 14 unbelted passengers and two flight attendants were injured during the incident, which occurred approximately four hours into the overnight flight.
Shortly after awakening from a “strategic nap” during a crew rest period (Air Canada allows pilots to nap in the cockpit), the first officer, looking ahead out the cockpit window, mistook the planet Venus for another aircraft to which the captain had called his attention. The startled first officer first pushed the control wheel of the Boeing forward to prevent what he believed to be an approaching collision, causing the aircraft to dive 400 feet. The captain recovered by pulling back on the control wheel, but not before the Boeing eventually climbed 400 feet above its assigned altitude of flight level 350.
The TSB found that the captain violated a number of Air Canada policies. The first officer, said the board, had rested much too long (75 minutes instead of 40), allowing him to enter deep sleep. Sleep inertia–the feeling of disorientation upon awakening–was the result the first officer experienced. The captain also failed to notify the cabin crew of the pilot’s nap, which would have suggested an extra check on passenger seat belts. Air Canada’s training was cited for not explaining why issues, such as sleep inertia, are important to crews.