The New Zealand Defence Force plane carrying New Zealand 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 Japanese Prime Minister Fumio Kishida and spend time promoting New Zealand trade.

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

The New Zealand Defence Force’s two 757 aircraft are over 30 years old and are becoming unreliable due to their age.

New Zealand Defence Minister Judith Collins told radio station NewsTalk ZB on Monday that the continued flight problems were “shameful” and that the ministry was now considering sending Luxon and his delegation on a commercial flight.

New Zealand’s defence force is struggling to maintain aging equipment and sufficient personnel. The government has said it would like to spend more on defence, but is also trying to reduce spending as the country faces economic challenges.