Four Australian crewmen feared dead after an army helicopter went down during joint military exercises have been named.
Captain Daniel Lyon, Lieutenant Maxwell Nugent, Warrant Officer Class Two Joseph Laycock and Corporal Alexander Naggs were on board the Taipan helicopter when it crashed in waters near Queensland's Hamilton Island about 10.30pm on Friday.
The MRH-90 helicopter had been conducting joint military training as a part of Exercise Talisman Sabre.
Australian Army chief Simon Stuart said the men were from the 6th Aviation Regiment based at Holsworthy Barracks in Sydney.
"They're part of a really tight team, a very highly professional, highly skilled aviation unit," he told reporters on Sunday.
"I couldn't be more proud of them - as professionals, as soldiers and as people."
Some debris from the stricken helicopter was recovered on Saturday and Queensland police urged members of the public who found crash material in the Whitsunday region to contact investigators.
Specialist navy divers have been assisting with the search on Sunday, while HMAS Brisbane and HMAS Adelaide have been deployed with sonar equipment.
An exclusion zone remains in place in waters south of Hamilton Island, from the southern tip of Long Island, east to Perseverance Island, south to Cole Island, and west to the mainland at Round Head.
Prime Minister Anthony Albanese thanked all those involved in the search, saying the incident was a stark reminder that there were "no safe or easy days for those who serve in our country's name".
"On behalf of our nation, our thoughts and prayers are with the families, friends and colleagues of those who are missing," he told reporters on Sunday.
Talisman Sabre director Damian Hill confirmed 47 MRH-90 helicopters had been grounded until further notice, although details of what might have led to Friday's crash have not been revealed.
It is the second time an Australian MRH-90 has been involved in an emergency this year after a Taipan ditched into waters off the NSW south coast in March.
The helicopter has earned a reputation as unreliable in recent years, with malfunctions and technical issues forcing several earlier groundings of the fleet.
Nationals leader David Littleproud called for an "open and transparent" inquiry into the incident.
"(We should be) making sure that we give our defence force the very best tools that they need to be able to defend us," he told Nine's Today program.
Labor frontbencher Michelle Rowland said the focus at this stage should be on the missing personnel and their families, but there would be a full investigation into what led up to the crash.
The Talisman Sabre training operation involves defence forces from Australia, the United States and other allies.
The joint exercises, which are mostly being held in regional Queensland, resumed late on Saturday in the Northern Territory and West Australia after an initial pause following the accident.
Lifeline 13 11 14
Open Arms 1800 011 046
© AAP 2023