By Neve Brissenden and Kathryn Magann in Sydney

A RECOVERY mission continues for three US marines killed in a chopper crash off the NT coast, as inquiries hope to determine why the aircraft ditched.

Of the 23 marines on the military Boeing MV-22B Osprey tilt-rotor aircraft, three were killed, one is in ICU, seven are in general hospital wards and 12 have been discharged.

“We’re incredibly lucky and incredibly thankful, for a chopper that crashes and then catches fire, to have 20 marines that are surviving, I think that’s an incredible outcome,” NT Police Commissioner Michael Murphy said on Monday.

The aircraft plunged to the ground on remote Melville Island, 80km north of Darwin on Sunday morning, sparking a significant rescue operation.

Twenty marines were transferred to Royal Darwin Hospital overnight, while rescue crews continued to work to recover the bodies from the crash site, which could take up to 10 days.

“This recovery and investigation will be prolonged, enduring and complex,” Mr Murphy said.

“We are planning to be at the crash site for at least 10 days.”

He said “absolutely everything” had been dedicated to the incident, to work out “the truth of what happened”.

NT Chief Minister Natasha Fyles said the territory was prepared for an incident of this scale and assured the families of the injured they were receiving good care.

“We do plan for these types of events, we hope that they never happen, but tragically when they do, we can respond,” Ms Fyles said.

“These people weren’t simply here for a few weeks on an exercise,” Ms Fyles said.

“They’re a rotational force that comes through the Top End every year and they integrate themselves into our community.

“They attend sporting events, they attend schools and they provide support, so they’re certainly part of our community.”

The Department of Defence said the incident occurred during Exercise Predator’s Run 2023 and no Australian members were involved.

The Marine Osprey aircraft has a tumultuous history, with a number of mechanical and operational issues since its introduction in the 1980s.

Since 2012, 19 people have died in six crashes involving the Osprey.

Australia’s Defence Force does not use the Osprey aircraft, an ADF spokesperson confirmed.

About 150 US marines are stationed in Darwin for the military drills alongside personnel from Australia, the Philippines, East Timor and Indonesia.

The exercises were paused after the crash but have resumed.

US President Joe Biden commented on the situation.

“Jill and I send our deepest condolences to the families of the marines who lost their lives in this deadly crash,” he posted to social media.

“We are praying for those who also suffered injuries.”

Prime Minister Anthony Albanese sent his condolences, adding the quick emergency response showed the “best of the Australian character”.

“We have no closer allies than the US. And this incident is, indeed, tragic,” he said in Perth on Monday.

The US embassy on Monday issued a statement thanking members of the rescue operation.

“Australians and Americans have been the closest of friends for over 100 years and we’re thankful for their continued friendship and support at this time.”

Relatives of those killed are being informed and a statement on the victims is expected on Tuesday.