Hundreds of air travellers had their flights delayed this morning after Air New Zealand's entire computer system failed.

Domestic and international flights were affected when power was cut to the airline's central computer facility in Auckland.

The outage affected online bookings, call centre systems and airport check in systems.

The company had to resort to manual bookings and check-in procedures while IT staff worked to fix the problem.

Queues of irate and frustrated passengers filled airport departure areas.

Even when the computer system was back up and running, at around 2pm, passengers were being warned that the backlog of delays would take "some hours" to clear.

Air New Zealand spokesman Bruce Parton said the airline was currently prioritising flights.