The Enhanced Air Cooperation initiative focused this year on fifth-generation fighter integration, aero-medical evacuation and aircraft maintenance.

Thousands of U.S. Marines on an Australian Army base this summer might be the most visible example of America’s growing military presence Down Under. But the nations’ air forces are growing equally close under a lesser-known program known as Enhanced Air Cooperation, or EAC.

The initiative, which kicked off in 2017, focused this year on fifth-generation fighter integration, aero-medical evacuation and aircraft maintenance. It involved U.S. F-22 Raptor, F-35B Lightning II, F-16 Fighting Falcon and F-15 Eagle fighters, B-52 strategic bombers and C-130J Super Hercules transports.

The Air Force’s activities in the Northern Territory, along with those of the Marines, are being supported with $2 billion worth of new military infrastructure funded by the U.S. and Australia, according to the Australian Defence Force.

At RAAF Darwin, for example, $88.65 million worth of projects have been awarded to build fuel tanks, expand the airfield and erect maintenance facilities.

These and other projects at RAAF Darwin are scheduled to be accomplished by 2023

“The major motivator for U.S. force restructure and redeployment on the western Pacific rim is China. It’s as simple as that”

The military buildup in Australia’s Northern Territory, which included a record number of U.S. Marines rotating there this summer, will continue as a response to growing Chinese capabilities, according to a former Australian defense official.

To support U.S. Air Force and Marine activities in the Northern Territory, Australia and the United States will invest about $2 billion on aircraft maintenance, support facilities, fuel storage and upgrades to accommodations, training areas and ranges.

The buildup in Australia’s Northern Territory will likely involve enhanced air and maritime facilities, Babbage said.

“It won’t only be the Marines,” he said. “It wouldn’t surprise me if the (U.S.) Army said they could send a couple of battalions (on a training rotation). Australia’s answer would be: ‘Of course you can come.’”

The U.S. Marines with 3rd Battalion, 12th Marine Regiment, a part of Marine Rotational Force-Darwin (MRF-D), fired Guided Multiple Launch Rocket System munitions, known as GMLRS, during Southern Reach, at Bradshaw Field Training Area, Northern Territory, Australia on August 15, 2019.

The HIMARS Marines fired two GMLRS in Australia for the first time ever, according to Cpl. Kallahan Morris. The HIMARS is a weapons system made up of the M142, five-ton chassis vehicle and can carry either a launcher pod of six rockets or one MGM-140 Army Tactical Missile System (ATACMS).

The live-fire training conducted was over an area of 3,282 square miles.

HIMARS is participating in MRF-D for the first time. These Marines and equipment provide MRF-D an extended range precision strike capability that can further shape the battlespace.

the HIMARS Marines with MRF-D conducted multiple fire missions, shot two GMLRS rounds, and enjoyed training in the heat of Australia’s Northern Territory dry-season.

America has allocated more than quarter of a billion dollars for Osprey aircraft infrastructure in Northern Australia.

The US Defence Department is looking to spend $305.9 million on facilities for their Osprey fleet, Chief Minister Michael Gunner told NT Parliament on Wednesday, while knocking back a suggestion that the money would be spent on a new naval base in Darwin.

"The budget appropriation that is being sought in America is for ramps for the Ospreys in the Northern Territory, not for a naval installation," Mr Gunner said.

"The Ospreys are aircraft vehicles. That is where the money is intended to go."

In July, the ABC revealed that a draft US Congressional bill had $US211.5 million allocated for new "Navy Military Construction" in Darwin, with few other details available.

Mr Gunner said that following these reports, he had reached out to US Secretary of Navy Richard Spencer, to clarify the nature of the spending.

The ABC understands plans for a new commercial port facility were still being discussed.

A draft defence bill tabled in the US Senate last month outlines that more than $300 million has been allocated for naval construction in Darwin, the ABC has reported.

The Australian Defence Department reportedly told the ABC that the proposed funding still has to be approved by Congress, but insists that any military projects are negotiated and agreed to by both governments.

Last month Defence and NT Chief Minister Michael Gunner rejected claims a top secret naval port is in the works at Glyde Point, north of Darwin, which could eventually help US Marines operate more readily in the Indo-Pacific.