New Zealand is gearing up to spend more than $2.3 billion on four new maritime surveillance aircraft. But that's the price of being about to watch on Blu-ray, rather than VHS.

The four Boeing P-8A Poseidon's will replace the ageing P-3K Orions, which are now more than 50 years old, and costing time and money in maintenance.

Defence Minister Ron Mark admitted to being a P-8 cynic before coming into Government, but said he believed purchasing the planes with the hefty price tag was the only sensible option.

SUPPLIED The US, Australian and Indian militaries brought their Boeing P-8A Poseidons to RIMPAC 2018.

New Zealand was not known for its military spending, but as tensions rise in the Asia-Pacific region, New Zealand is in the process of updating its maritime capabilities, and the government is using the opportunity to upgrade.

READ MORE:

* Pacific Rim countries join forces as tensions rise

* China sends spy ship to Hawaii military exercise

* New sub-killer planes may never fire in anger

As well as the P-8s, the country's two frigates are undergoing an upgrade. It was originally priced at $446 million, but the costs blew out, and last year the Government approved a further $148m in spending.

SUPPLIED New Zealand will spend more than $2.3 billion on buying four of the aircraft to replace its P-3k Orions.

The jump in spending comes as the government releases its rebooted defence white paper, which makes a clear foreign policy statement, and draws attention to a range of factors the Government believes are threatening the rules-based order - primarily China's rise.

Defence procurement critics, including Green Party MP Golriz Ghahraman, and former Green Party MP Keith Locke, say New Zealand should not be increasing its military spending to fund planes with greater warfare capabilities.

VHS OR BLU-RAY

SUPPLIED The planes, which will begin to be delivered and brought into service by 2023, are known for their submarine-hunting capabilities.

Those on the ground say they will be sorry to see the P-3s go, but they're past their use by date.

The P-3s have been around for so long, one person in Squadron 5 (the P-3 squadron) can tell stories of when his father flew the planes.

They were supposed to last just 30 years, and while they could still functionally do the necessary jobs - search and rescue, fishing surveillance, anti-piracy and anti-smuggling, anti-surface warfare, anti-submarine warfare - the P-3s have seen their best years.

SUPPLIED While those on the ground see the benefits of the hefty purchase, some believe the high-capability aircraft has more than New Zealand needs.

RNZAF Wing Commander (WGCDR) Peter Gibson, who is working alongside the US P-8s at the Rim of the Pacific (RIMPAC) maritime training exercise in Hawaii, said the difference between the two aircraft was like the difference between watching a movie on VHS or Blu-ray DVD.

"You're doing the same thing but you're using much more modern technology."

Then there's the smell - the P-3s smell like "50 years of farts and smelly guys", Gibson says.

SUPPLIED The body of the aircraft - made by Boeing - is the same as the airliner's 737s

THE SUB-HUNTERS

The P-8s certainly don't smell like farts and sweat. Walking onto the plane is much like embarking on a commercial flight.

The body of the aircraft - made by Boeing - is the same as the 737 commercial airliner. But rather than an interior filled with seats and luggage compartments, it has windows built for surveillance, five large screens along one wall, a teched-out cockpit, and row-upon-row of sonobuoys - lined up to be deployed through any number of chutes in the hopes of detecting a ship, or maybe a submarine.

SUPPLIED Golriz Ghahraman and Keith Locke say New Zealand should not be increasing its military spending to fund planes with greater warfare capabilities.

The planes, which will begin to be delivered and brought into service by 2023, are known for their submarine-hunting capabilities. And as the waters in the wider Indo-Pacific region become busier and in some places contested, the ability to better locate submarines is being seen as necessary by an increasing number of countries.

As China's aggression over its perceived claim to the South China Sea increases, the United States and partner nations, including Australia, the UK, and New Zealand - as well as Norway, India and South Korea have made the choice to purchase the sub-hunters.

The sonobuoys are deployed out of the plane and activate when they hit the water. They then send down a microphone on a string, which can record the sound of a ship or a submarine in the area.

US NAVY/ SUPPLIED Tim Groser, New Zealand Ambassador to the United States and Wing Cmdr. Peter Gibson.

It can also send out a sonar signal, which will ping back when it hits something, which allows the crew to determine the distance of an object.

The crew aboard the US P-8 stationed at Hickam in Hawaii doesn't want to give away too much in terms of operational strategy, but the P-8 crew says they are able keep their presence hidden from any subs, or make themselves known.

In some situations, the P-8 crew will surround the sub with sonobuoys and continuously ping the submarine with signals, until it moves on - hopefully.

US NAVY/SUPPLIED New Zealand is gearing up to spend more than $2.3 billion on four new maritime surveillance aircraft. But that's the price of being about to watch on Blu-ray, rather than VHS.

Gibson says the crew relies on good intelligence to find the submarines, and will usually try and locate them in a "chokepoint".

Scanning the ocean for subs would be like trying to find a needle in a haystack.

Senior National Officer Group Captain Daniel Hunt, who is director of the RIMPAC Combined Air Operations Centre - responsible for more than 200 aircraft - said the P-8s were versatile when it came to maritime surveillance - from search and rescue, or counter-piracy through to anti-submarine warfare.

STUFF Kiwis participate in RIMPAC, Rim of the Pacific, the world’s largest international maritime training exercise.

"You use the same skills; you use the same sensors, you just deploy them in a slightly different way to achieve a slightly different effect."

New Zealand had established a strong reputation thanks to its deployments of the P-3s to the Middle east and South pacific, he said.

"The P-8's going to enable us to maintain that credible, international party status now, and in the decades to come."

Meanwhile, Captain Blair Gerritsen, who is RIMPAC's Sea Combat Commander, said there would always be a use for maritime surveillance aircraft, especially given the size of New Zealand's area of responsibility.

FUNDING THE WAR INDUSTRY

While those on the ground see the benefits of the hefty purchase, some believe the high-capability aircraft has more than New Zealand needs.

Former green party MP Keith Locke said the purchase was New Zealand's way of "cosying up" to the US.

"New Zealand could have bought four high-tech surveillance planes, without the anti-submarine capacity, at a fraction of the cost, and they would have been much more useful to New Zealand," Locke said.

"The more our surveillance planes are geared for war-fighting, the less they'll be available for monitoring fisheries in the South Pacific and Antarctica.

"Much of the time they'll be off conducting anti-submarine exercises with the other Five Eyes nations, or flying alongside American planes in Middle Eastern surveillance missions."

Green Party defence spokesperson Golriz Ghahraman said New Zealand was undermining the global objective of weapons non-proliferation by investing in the war industry.

CHANGES AFOOT

Meanwhile, Wing Commander Aaron Young, who's in charge of New Zealand's two P-3K2s at RIMPAC said the P-8s would mean a big change for Squadron 5.

Young would be saying goodbye to his trade as a flight engineer - the P-8s don't have flight engineers in the crew - and Squadron 5 would be moving from Whenuapai air base to Ohakea, which could see some people leave the Air Force.

But Young said the aircraft were nearing the end of their life and it was timely to replace them with something that could get to a location quicker, stay there longer, and was logistically cheaper.

TOP BRASS TIGHT-LIPPED

Kiwis in positions of authority at RIMPAC were quick to talk about how New Zealand's capabilities held their own.

When asked about why the upgrades and increased defence spending was necessary, they close up, saying that is a decision for the Government.

Australian Navy Commodore Warfare Commodore Ivan Ingham - part of RIMPAC's senior leadership - said the Te Mana (one of New Zealand's soon-to-be-upgraded ANZAC frigates) was a "very capable ship".

"But it's not really up for me to say whether the performance of the ship provides some sort of a justification about the upgrade programme - that's a matter for the new Zealand Government," he said.

But everywhere at RIMPAC people are talking about the rise of China in the region, and the potential escalation of tensions in the South China Sea. Even New Zealand has joined the chorus of voices talking about the threat to the rules-based order.

But the hope of some people working in the Asia-Pacific security space, is that while countries in the region prepare for the worst, it doesn't become a self-fulfilling prophecy.

- The writer's trip to RIMPAC was funded by the US Government