The Prime Minister is defending the deployment of a second Defence Force plane for his Pacific Islands Forum mission, having previously criticised the use of a back-up plane when in opposition.

Christopher Luxon is in Palau for the annual PIF leaders meeting. Both RNZAF Boeing 757s have been deployed on the mission, with one staying in Cairns as a back-up.

Luxon said it was a Defence Force decision to take two planes, with 88 people from New Zealand heading to the meeting.

"We've taken 14 delegations up here, we've got a lot of people to take home on Sunday as well, and we're taking some home when I go out on Friday as well."

Luxon said connectivity was a big challenge at PIF, and had talked about the importance of connectivity at the realm leaders meeting with Tokelau, Niue and the Cook Islands last week.

"It makes the case for why we need a good, reliable Air Force plane."

Air Component Commander Air Commodore Andy Scott also spoke of the PIF meeting's remote location.

"This important meeting is being held in a comparatively remote location where air services and options are limited, and therefore a back-up aircraft has been positioned to assist if required for any reason."

New Zealand is hosting next year's meeting.

In 2023, the Defence Force sent a back-up plane for then-Prime Minister Chris Hipkins' trip to China.

That plane, which was sent in case the first broke down, was left in Manila. This attracted strong criticism from then-opposition and National Party leader Luxon, who said it "doesn't seem a good move" in a climate challenge.

Labour leader Chris Hipkins (right) says Christopher Luxon is changing his position based on what is convenient for him. Photos: RNZ

Luxon vowed not to use Defence Force planes to travel internationally if he became Prime Minister - a promise he quickly reneged on.

On Thursday, Hipkins said Luxon was changing his position based on what was convenient for him.

"Well, well, well," he said. "Hypocrisy knows no ends."

Labour deputy leader Carmel Sepuloni alleged the second plane was taken because of a breakdown in the relationship between Luxon and Foreign Affairs Minister Winston Peters.

Peters, who had been in Palau earlier in the week, returned to Parliament on Thursday.

Foreign Affairs Minister Winston Peters defended the use of two planes. Photo: RNZ

Sepuloni said Luxon and Peters could have flown together, without the need for a second plane.

"It's like a couple who have separated who can't stand to be in the same room, or something. So in this instance, they can't even share the same plane, they couldn't align their timing for travel. It is bizarre."

Sepuloni said that was a "theory" and she had "heard some murmurings" around Parliament, but would not back her claim up.

But Peters said it was "totally untrue", and the plane was also used to transport other leaders.

"Carmel can do better than that, surely. The last time Palau had [the PIF] there were only eight countries. Because of New Zealand, there were 18 countries there.

"And the second thing is we can't afford, if any mistake goes, to have them parked up then can't get home. So we've got a plane in Australia just in case the contingency happens. That's a Defence matter, but it makes sense."

History of planes breaking down on PMs

The government is purchasing two new Airbus A321XLR planes on a lease-to-buy arrangement to replace the ageing 757s.

The current planes, which were purchased in 2003, are mostly used for transporting cargo around the Pacific. But they have a recent history of unreliability when it comes to prime ministerial travel.

In 2024, Luxon had to fly commercially to Melbourne after the 757 broke down.

He also left a business delegation in Papua New Guinea after a 757 broke down during a refuel stop en route to Japan.

In 2016, Sir John Key was forced to cancel the first day of a trip to India after the 757 broke down in Townsville, while in 2019 Dame Jacinda Ardern flew commercially back from Melbourne after a breakdown.

She also took a commercial flight back to New Zealand from the United States in 2022 when the 757 broke down in Washington DC.