A pilot has admitted falling asleep twice while at the controls of an Air New Zealand Boeing 777-300 aircraft on a flight from London to Los Angeles.
The incident which occurred in November 2011 was reported to the Civil Aviation Authority at the time.
The pilot, whose name has been withheld by the authority, describes already feeling tired when he arrived in London.
Once there, he says he was forced to change hotel rooms three times in two days.
Not long after take-off the pilot reported that he suddenly and without warning fell into a deep sleep while on the flight deck and later did that again.
The long-haul Boeing 777-300 is one of the largest aeroplanes in the airline's fleet and is capable of carrying just over 300 passengers.
Air New Zealand said the flight was being operated by three pilots. During the cruise phase one of the two operating pilots nodded off twice for about a minute and woke spontaneously. The other operating pilot on the flight deck was aware of this and safety was not compromised at any point.
A spokesperson said safety is paramount for the airline which recognises the risks of crew fatigue, and as part of its safety culture it supports and encourages staff to self report incidents of fatigue, which is what occurred in this case.
Air New Zealand said the pilot will not face any disciplinary action because that would be counter productive, although it will not say whether he is still flying long-haul trips.
The CAA says it is up to the airline to investigate the incident.