It is understood the aircraft crashed off the coast of Shoalwater Bay near Rockhampton in North Queensland in the late afternoon on Saturday.
Australia's Minister of Defense Marise Payne said no Australian Defense Force personnel were onboard the aircraft at the time. Bonhomme Richard, part of a combined U.S. -Australia-New Zealand expeditionary strike group, is undergoing a series of scenarios that will increase naval proficiencies in operating against blue-water adversarial threats and in its primary mission of launching Marine forces ashore in the littorals.
"The exercise was to prove (Australian personnel) could operate a broad a range of aircraft", commander Adrian Capner said.
The Osprey is a tilt-rotor aircraft that takes off and lands like a helicopter, but flies like an airplane.
Iran accuses USA navy of firing warning shots at its vessels
In a similar incident , the USS Thunderbolt fired warning shots at Iranian navy boats operating in the Persian Gulf on Tuesday. There have been a string of close encounters between USA ships and Iranian vessels in the Gulf in recent months.
Three service members are missing after a Marine Corps aircraft carrying more than two dozen people crashed off the Australian coast on Saturday.
Three people are reported to be missing, feared dead, while up to 20 people have been rescued, according to the Courier-Mail. Since becoming operational in 2007 there have been five further crashes and several other incidents that have resulted in a further nine deaths. "The United States are leading the search-and-recovery effort", Payne noted in her statement.
"I have briefed Prime Minister (Malcolm) Turnbull and spoken with Secretary Mattis this evening to offer Australia's support in any way that can be of assistance". They are much faster than helicopters and have the capability to move vertically.
Last December, a United States military Osprey crash-landed off Japan's southern island of Okinawa.