Science of fatigue

In 1996 – around the same time Canada last updated fatigue rules for pilots – NASA published new research on pilot fatigue, conducted by global experts in fatigue science. Recognizing that the aviation industry requires 24-hour activities to move people and cargo, they developed an extensive set of guidelines for duty and rest scheduling in commercial aviation, based on science and the experience of pilots.


  • Losing as little as two hours of sleep will result in acute sleep loss, which will induce fatigue and degrade performance and alertness.
  • The physiological need for sleep created by a deficit (where you body continually receives less sleep than required) can only be reversed by sleep.


Your body clock, also known as circadian rhythm, provides a high level of functioning during day that counteracts the ability and desire to sleep.

  • Therefore, circadian disruption can lead to acute sleep deficits, cumulative sleep loss, decreases in performance and alertness, and various health problems.
  • Your “window of circadian low” is calculated from scientific data on the circadian low of performance, alertness, peak fatigue, and body temperature.
  • For flight duty periods that cross three or fewer time zones, the window of circadian low is estimated to be 0200 to 0600 home-base time.


Additional flight crew afford the opportunity for each flight crew member to reduce the time at the controls and provide for sleep during a flight duty period.

  • However, controlled rest on the flight deck (when a pilot takes a short nap to mitigate fatigue) is not a substitute for the sleep opportunities or facilities required for additional flight crew members.


Read excerpts from the research