WELLINGTON - The New Zealand defense force plane flying New Zealand's Prime Minister Christopher Luxon to Japan broke down on Sunday, forcing the Prime Minister to take a commercial flight, his office confirmed on Monday.

Luxon is spending four days in Japan, where he is expected to meet with Japan's Prime Minister Fumio Kishida and spend time promoting New Zealand business.

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New Zealand media reported that the Boeing 757 broke down during a refueling stop in Papua New Guinea, leaving the business delegation and journalists stranded in Port Moresby, while Luxon flew commercial to Japan.

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The New Zealand Defence Force's two 757s are more than 30 years old and their age has made them increasingly unreliable.

New Zealand Defence Minister Judith Collins told radio station Newstalk ZB on Monday that the consistent flight issues were "embarrassing" and that the ministry was looking at flying Luxon and his delegation commercially from now on.

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New Zealand's defense force is struggling with aging equipment and retaining sufficient personnel. The government has said it would like to spend more on defense but is also trying to reduce spending as the country faces economic headwinds.