The pilot of a Boeing 777 nodded off during a flight between London and Los Angeles.
Air New Zealand said the pilot had reported falling asleep twice as he flew the plane across the Atlantic in 2011.
The company said the incident did not compromise the safety of passengers, as the pilot was not alone on the flight deck.
But New Zealand transport minister Gerry Brownlee said that it “doesn’t look good” for the airline.
He is reported as saying: “You’ve got big reputational issues here. Satisfy the public that you’re making sure your pilots are not asleep on the job.”
New Zealand media yesterday said details emerged only after a request was made under the official information act.
In a statement, Air New Zealand said: “During the cruise phase of the flight one of the two operating pilots nodded off twice for around 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.”
Most large aircraft have autopilots which help to control the aircraft, often during long periods of flying at the same altitude on long-haul flights.
According to a report, a New Zealand Civil Aviation Authority document said the unnamed pilot had voluntarily submitted a fatigue report, blaming a bad night’s sleep in London.
It is understood the pilot will not face disciplinary action, as the airline does not wish to discourage pilots from reporting such incidents.