NZ Defence Force plane breaks down ahead of Jacinda Ardern's Melbourne trip

A Defence Force plane set to take Prime Minister Jacinda Ardern to Melbourne this week has broken down.

The Prime Minister was due to fly to Melbourne on an Air Force Boeing 757 on Thursday morning to meet her Australian counterpart Scott Morrison, but it's broken down and may not be able to fly.

The New Zealand Defence Force has two 757s used for transporting VIPs.

A Defence Force spokesperson said one was in scheduled maintenance but the other was in Australia undergoing "unscheduled maintenance".

"The repair is due to be carried out tomorrow and the aircraft is scheduled to be available for the Prime Minister's flight on Thursday."

This is not the first time the 757s have let our politicians down - former Prime Minister John Key had to be rescued back in 2016 when a 757 broke down twice, stranding him and a delegation of nearly 100 in Townsville, Australia en route to India.

Last month, a second plane had to be sent to pick up Deputy Prime Minister Winston Peters when one of the 757s broke down in Vanuatu.

The Government is replacing its five ageing C-130 Hercules Defence Force planes and six ageing P-3K2 Orion maritime patrol aircraft, but there are no plans yet for the 757s.

Unless we want to keep stranding politicians all over the world, perhaps it's time.