Air New Zealand on Thursday said a Boeing 777 pilot fell asleep in the cockpit during the flight from London to Los Angeles but said safety was not compromised.
The airline said the pilot reported falling asleep twice during the flight over the Atlantic in 2011 but said he was not the only pilot on the flight deck.
A New Zealand Civil Aviation Authority (CAA) document said the pilot, who has not been named, blamed having to change hotel rooms three times during the night because air-conditioning problems.
Transport minister, Gerry Brownlee said the incident does not bode well for the reputation of the airline.
"You've got big reputational issues here. This doesn't look good. Satisfy the public that you're making sure your pilots are not asleep on the job," he said.
New Zealand media said details only emerged after a request to the CAA under New Zealand's official information act.
Air New Zealand's Chief pilot David Morgan said the pilot in question fell asleep for about a minute on each occasion.
"Yeah, oh just briefly, around about a minute, a minute and a half on both occasions," he said.
The reason we do this reporting is so that we can better manage the business and learn from events such as this," Morgan added.
Local media quoting Air New Zealand said the pilot would not face disciplinary action as it wants staff to be confident that they can report similar incidents.
Presented by Adam Justice