Narrative:

Aircraft had a maintenance issue; the APU generator kept tripping off; and company finally decided to switch aircraft. We finally departed close to xa:00; about 1.5 hours before our duty cco ran out. During the pre-departure brief we talked about the late hour and fatigue being a threat. Once we were in cruise flight we both felt very tired and talked about how we wished we had an international relief officer (international relief officer) so that we could get a break and some sleep. About 3-4 hours into the flight I accidentally nodded off. I am not sure how long I was asleep; but it was probably not more than 5-10 minutes. When I woke up; I noticed the first officer had accidentally fallen asleep as well. Both pilots had fallen asleep at the controls! These late departures unaugmented are bad enough; but when you have a delay that lasts several hours; they are downright dangerous. Even if you feel ok at departure; you can 'crash' a few hours into the flight. I had taken a short nap about 5 hours before check-in; but was still very tired after take-off. Thankfully; nothing bad happened; but the potential for a dangerous situation was there.

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Original NASA ASRS Text

Title: B757 Captain reported that flight delays and fatigue caused him and the First Officer to fall asleep during flight.

Narrative: Aircraft had a maintenance issue; the APU generator kept tripping off; and company finally decided to switch aircraft. We finally departed close to XA:00; about 1.5 hours before our duty CCO ran out. During the pre-departure brief we talked about the late hour and fatigue being a threat. Once we were in cruise flight we both felt very tired and talked about how we wished we had an IRO (International Relief Officer) so that we could get a break and some sleep. About 3-4 hours into the flight I accidentally nodded off. I am not sure how long I was asleep; but it was probably not more than 5-10 minutes. When I woke up; I noticed the First Officer had accidentally fallen asleep as well. Both pilots had fallen asleep at the controls! These late departures unaugmented are bad enough; but when you have a delay that lasts several hours; they are downright dangerous. Even if you feel OK at departure; you can 'crash' a few hours into the flight. I had taken a short nap about 5 hours before check-in; but was still very tired after take-off. Thankfully; nothing bad happened; but the potential for a dangerous situation was there.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.