Three US Marine Corps troops died on Sunday after a military aircraft crashed near Darwin, Australia, during a routine training exercise. Five others have been transported to the Royal Darwin Hospital in serious condition.

The aircraft, an MV-22B Osprey that was transporting troops, crashed on Melville Island at 9.30am with 23 personnel on board, according to a statement from the Marine Rotational Force. That force has deployed to Australia every year since 2011 and now consists of 2,500 Marines.

The Marines were taking part in Exercise Predators Run, according to the statement, a joint military exercise also involving soldiers from the Philippines, Indonesia and East Timor.

Recovery efforts are continuing, and an investigation into the cause of the crash is underway, the statement said.

The Osprey is an especially complex aircraft with a troubled history. With two rotor blades above extended wings, it takes off like a helicopter and can fly like a fixed-wing aircraft — which means that pilots need expertise in both.

It has been used by the Marine Corps since the early 1990s, but in 2000, the fleet of Ospreys was grounded after two crashes, including one at night over North Carolina that killed all four Marines on board.

Last year, nine Marines were killed in two separate crashes. One Osprey aircraft crashed in June during a training mission near Glamis, California, killing five. Another crashed in a valley in Beiarn, Norway, killing all four on board.

Prof. Peter Dean, the director of foreign policy and defence at the United States Studies Centre at the University of Sydney, said the Ospreys had become less problematic over time, and some studies suggest they are no riskier than other combat aircraft, but the crash on Sunday would once again raise doubts about their safety.

Prime Minister Anthony Albanese said that the crash was “tragic”, and that the Australian authorities were focused on “making sure that every support and assistance is given at this difficult time”.

It is the second fatal accident involving aircraft and joint training between the US and Australia this year. In July, an Australian Army MRH-90 Taipan helicopter crashed into waters near the Whitsunday Islands, more than 1,000 miles east of Sunday’s Osprey accident, killing four Australian defence personnel.

New York Times News Service