The Prime Minister is expected to travel to the Pacific later this year in one of the Defence Force's ageing C-130 Hercules aircraft - the entire fleet of which has been grounded.
Defence Minister Ron Mark said on Thursday at a select committee that New Zealand did not have a single C-130 Hercules aircraft available for use.
He told MPs at the hearing: "This is what happens when successive Governments defer decisions and defer decisions, and aren't brave enough to make the big spend when it's needed."
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Newshub previously revealed last year that, at any one time, more than half of the old Hercules fleet had been grounded due to repairs.
The Defence Minister was referring to the Government's commitment to spending more than $1 billion to replace New Zealand's five ageing C-130 Hercules Defence Force planes with new C-130J-30 Super Hercules aircraft.
Chief of Defence Force Kevin Short told Newshub after the hearing that the Defence Force has struggled to have two of the aircraft available at any given time.
Prime Minister Jacinda Ardern has insisted that replacing the old Hercules aircraft is necessary, because "without it we just couldn't look after ourselves and our neighbours".
Purchasing the new C-130J-30 Super Hercules aircraft has been earmarked as a high priority project within the Government's 2019 defence spending plan.
Ardern is expected to be travelling to the Pacific at the end of the year in one of the aircraft. Mark said he was confident she would be safe, despite the planes showing signs of unreliability.
"I have total confidence the air force [part of the Defence Force] would not put an airframe into the air that they did not have confidence in, end of story," Mark told Newshub.
Short said it's unusual to have all of the C-130 Hercules aircraft grounded at the same time. He said of all the capabilities of the Defence Force, "the Hercules has been one of those that respond to just about every task that we have".
"We do have indications that the first one will come up in Australia at the end of today but it really just highlights the age of the aircraft themselves, the increased likelihood they will break, and the increased costs of actually keeping them maintained."
He said the Defence Force still has Boeing 757s, "so we look at the complete transport fleet and the way we can provide support whatever the tasking is - so it's not just the C-130s".
Pointing to the need to upgrade the Hercules planes, Short said: "You imagine keeping a car that you might have for 55 years and use if for everyday use - it costs a lot of money and takes a lot of effort - and it's no different with aircraft."
Mark said the entire Hercules fleet's grounding was "a little reminder as to how vulnerable we are and how important it was we make a decision and we move".
"I've actually had my head inside the wing of a Hercules that was under maintenance and had technicians pointing out to me some of the issues that they're now having to deal with that they've never seen before."
Mark said the ageing Hercules aircraft are "going to become more expensive to run and that's why it's imperative to go for the C-130J-30 Super Hercules".