Human error was to blame for a deadly US Marines Corps aviation crash in the Northern Territory last year, an official report has found.
Three marines died and 20 others were hospitalised after the MV-22B Osprey went down on Melville Island, north of Darwin, last August.
The tiltrotor aircraft was taking part in Exercise Predators Run, run by the Australian Defence Force.
Leading up to the disaster, the Osprey had a mixed safety record, but the US Marines' official investigation ruled out "material or mechanical failure" for the Melville Island crash.
The US Marines say the human error was due to the pilot losing "situational awareness".
"During the flight's final approach to the precoordinated landing zone, the aircraft executed three extreme right banks, causing an aerodynamic stall condition.
"Follow-on flight manoeuvres were not able to recover the aircraft, resulting in the crash."
The investigators also praised the response of Australian military units and civilian emergency services to the crash who they say helped save lives.
Two Marines were killed by the August 27 crash, pilots Captain Eleanor V. LeBeau, 29, and Major Tobin J. Lewis, 37. A third Marine, crew chief Corporal Spencer R. Collart, 21, was killed as he "heroically re-entered the burning cockpit of the aircraft in an attempt to rescue the trapped pilots," the investigators said in its report.
The NT accident exposed significant safety issues within the US Marines squadron, the report said. Investigators recommended punitive actions, including potential court martial charges for one senior squadron member and potential administrative actions against the squadron's former commanding officer.
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The Osprey, which is able to fly both as an airplane and helicopter, has been involved in four fatal accidents in the past two years that have drawn renewed scrutiny by US authorities.
The aircraft has been a vital asset in US special operations and combat missions, but it is considered one of the most complex aircraft to fly and maintain, and it has a troubled accident history.
- With Associated Press