According to the report, the first officer had slept 75 minutes, and was suffering from "sleep inertia" and fatigue. Canadian regulations permit 40-minute naps, and pilots and co-pilots are supposed to be allowed an extra 15 minutes once awake to regain full alertness. U.S. rules do not allow in-cockpit naps.
"This occurrence underscores the challenge of managing fatigue on the flight deck," said lead investigator Jon Lee in a statement.
ABC News explored the connection between pilot sleep, or the lack of it, and air safety, in a series of reports in 2011.
In the U.S., more than two dozen accidents and more than 250 fatalities between 1991 and 2011 have been linked to pilot fatigue, according to the National Transportation Safety Board. The NTSB investigation into the Feb. 12, 2009 crash of Continental 3407, operated by Colgan Air, near Buffalo, N.Y., determined that both pilots were sleep-deprived at the time of the crash.
"Well-rested pilots are very important because studies have shown that being tired is equivalent to being drunk," said Mary Schiavo, former Inspector General of the Transportation Department. "In fact in recent studies, including by Harvard, Stamford, and others have shown that pilots that are sleep deprived behave as someone who has had a few drinks."
"Fatigue has a big impact on your ability to perform," said human fatigue expert Dr. Martin Moore-Ede, CEO of Circadian Technologies. "You might say that fatigue makes you stupid. In other words, all the things you learned in your training, in your hours in the simulator ... those things tend to fall away when you're in a fatigue state."
While the FAA has imposed some new rules to fight pilot fatigue, it did not address the problem of pilots who commute long distance to their bases, often spending the night in crew lounges, or in so-called crash pads near the airport, where quality sleep can be elusive. Both pilots in the Colgan crash were "commuters" who had slept in the airport crew lounge before the fatal flight.