About 160 of Air New Zealand's international and domestic flights had been affected. As the international flights cleared, cancellations were announced for a raft of domestic routes. Passengers have been left stranded and looking to Air New Zealand for answers.
First reports of problems came through about 2.50pm. Airways New Zealand reported that the radar problem was partially fixed at 4pm and was completely operational again at 4.30pm.
Transport Minister Simon Bridges said there had been an "outage to the nationwide air radar network". He said the cause was unknown.
During the outage, all departures were suspended and the landing of any incoming aircraft was staggered. Air traffic control had been able to communicate with any incoming planes via radio contact. Mr Bridges said he had been assured passengers were never at risk.
A spokeswoman for the Dunedin airport said an Air New Zealand ATR, a Jetstar A320 and a Virgin Boeing 737 had to wait on the tarmac this afternoon. Up to 400 passengers were affected. The departure of the Virgin flight to Brisbane in Australia had been delayed since 3.30pm.
The airport's website showed that Air New Zealand flight 8095 from Christchurch to Dunedin had been cancelled.
Queenstown Airport Corporation chief executive Scott Paterson also confirmed the "very unusual'' fault had affected the resort town's airport, holding up departures while inbound flights were able to land.
Fortunately the airport had a quiet schedule this afternoon, he said, but it would have been a different story from next week on, as the ski season got into full swing. "This time next week or the week after, we would have been very anxious.''
At Christchurch airport, Geoff Neilson decided against waiting for a new flight to be scheduled and planned on renting a car to drive to Dunedin.
"We can hire a car and be well on the road but the time things are sorted here. There's nothing you can do about it."
Network error at Airways
The radar outage was caused by an internal system network error at Airways New Zealand, a Civil Aviation Authority spokesman said this evening.
Flights were resumed on a priority basis, with major trunk routes and jet flights taking off first.
The CAA will investigate the cause or causes of the radar fault and work on a solution to prevent another outage.
Big backlog
Air New Zealand flights out of Auckland, Christchurch, Tauranga and Wellington were among those cancelled today. A statement from Air New Zealand said it would take some time to clear the backlog of delayed flights.
The national carrier advised passengers to check arrivals and departures information on its website or download the Air New Zealand app for up to date information on any ongoing disruptions.
A Jetstar spokesman said the radar fault affected a total of seven flights, with the longest delays up to 1 hour and 15 minutes.
An Auckland Airport spokesman said there was no congestion in its terminals following the outage, which affected 20 domestic and five international flights.
Passengers stranded
At Auckland airport, Hemi Takarua had just learned the 4.10pm flight to New Plymouth had been cancelled. He said he was stranded and hoping Air New Zealand would compensate him for the delay.
"If I'm staying tonight, Air New Zealand should pay. It was just a day trip for me. I've got to go home ... I've got to go to work."
Brent Snooks was on the same flight and was lining up to try and find another way to New Plymouth. "They haven't really offered any sort of alternate transportation to get down, or accommodation for overnight."
Jill Dixon and her grandson Jacob Ellery said their flight to Tauranga was cancelled this morning for unexplained reasons - and then the radar glitch hit, delaying a second flight. She and Jacob learned only a few minutes before boarding a 3.35pm flight that they would have to stay put.
Ms Dixon, of Palmerston North, said Air New Zealand should put them up for the night and pay her airport parking fees which she estimated had increased by $45.
Brisbane resident Anna Lane had planned to fly from Wellington to Napier to visit her mum, who is recovering from a hip operation. She said she only just arrived in Wellington when she found out her next flight was cancelled.
As it became clear international flights would take priority, Ms Lane said she expected to be delayed for hours. She said she would hire a car and drive to Hawkes Bay rather than spend a night in Wellington.
- additional reporting by NZ Herald and NZME News Service.
