Missing Marines unlikely to be found alive: authorities

AAP

Three Marines missing after a US military aircraft crashed off the Queensland coast are unlikely to be found alive, with the search now becoming a recovery operation.

Search and recovery operations were suspended on Sunday, less than 24 hours after the tilt-rotor aircraft MV-22 Osprey crashed off Shoalwater Bay, on the central Queensland coast, with 26 personnel on board.

The ship's small boats and aircraft rescued 23 personnel, with one taken to hospital in Rockhampton with a fractured leg, while three are missing.

US military officials, who described the crash as a "mishap", have turned their efforts to salvage and recovery, which they warn could take several months.

It is unlikely that the three missing US marines will be found alive, officials say. Photo: AP

The missing marines' next-of-kin have been notified.

The Osprey launched from the USS Bonhomme Richard on Saturday afternoon during regularly scheduled operations and went down while trying to land.

The aircraft is believed to have crashed into the flight deck and slid into the ocean.

The weather is not believed to be a contributing factor to the crash, The Herald Sun has reported.

A MV-22 Osprey tiltrotor helicopter went down at Shoalwater Bay near Rockhampton. Photo: Getty

It is the 10th known crash involving an Osprey - a tilt-rotor aircraft that takes off and lands like a helicopter but flies like an aeroplane - since 1991.

The federal government confirmed no Australians were on board the aircraft and said the Defence Force would assist US Navy and Marine Corp recovery efforts.

US President Donald Trump and Prime Minister Malcolm Turnbull were briefed on the incident and Queensland Premier Annastacia Palaszczuk offered her government's support.

Marine Corps confirmed there was an active search and rescue mission after the MV-22 Osprey went down. Photo: Getty