Our Hercules planes are "falling apart" and an upgrade is long overdue, ACT Party defence spokesperson Dr James McDowall says.
It comes after Prime Minister Jacinda Ardern had to take an Italian government Hercules home from Antarctica after New Zealand's plane broke down.
McDowall said it was a "bad look" for the prime minister to hitch a ride on another country's aircraft.
A New Zealand Defence Force spokesperson earlier blamed breakdown on the C-130H being on the ground in Antarctica for two days.
Air Commodore Shaun Sexton said because of the cold, a breakdown in Antarctica wasn't "completely unusual".
"We have special procedures to manage the cold and the harsh environment, but unfortunately in this case those procedures didn't create the outcome we want," he said.
Usually, the issues were mitigated by propeller heaters being used and a methodical pre-flight process used to warm the aircraft to a suitable operating temperature.
The C130H will be repaired and is expected to return to New Zealand in the next few days, the Defence Force said.
But McDowall said repeated breakdowns just emphasised "how out of date our fleet is".
But it also spoke to a wider issue in New Zealand's defence, he said.
"We are actually quite vulnerable in a in a combat situation."
New Zealand had limited ship capabilities and "a couple of ageing frigates", McDowall said.
"It just shows our allies, especially our Five Eyes allies, that we're just not taking this stuff seriously, and at some point they're just going to get sick of us not making contribution."
Sexton said the Hercules aircraft had been in service with the Air Force "for some 60 years" and have done "outstanding work" in the Pacific and around the globe during that time.
Like with anything mechanical of age, there could be "challenges", but the maintenance and engineering people in true "Kiwi spirit" kept the engines running, he said.
The Ministry of Defence has already announced that the Hercules are to be replaced by new Lockheed Martin C-130J Super Hercules aircraft.
But the five new aircraft were not expected to be fully operational until 2025.
In addition the first of four P-8A Poseidon aircraft for maritime patrol would arrive by the end of this year, with the rest early next year, Sexton said.
But McDowall did not believe that was enough.
ACT thought New Zealand should follow the NATO target and methodology.
"The target of two percent of GDP is what all of our traditional allies, including Australia, are committed to and would demonstrate the seriousness with which we take our defence obligations," McDowall said.