Deputy Prime Minister Michael McCormack is holding out hope Malaysia Airlines flight 370 may one day be found, as a search for the plane draws to a close.
A search of the seabed in the remote Indian Ocean where the aircraft is believed to have crashed ends on Tuesday, after two extensions of the original 90-day time limit.
Mr McCormack said all Australians were feeling for the loved ones of those on the ill-fated flight, after a four-year search costing more than $200 million failed to find the wreckage.
"It's very sad for the families and relatives of the 239 people on board, particularly the seven Australians," he told Sky News.
The Boeing 777 vanished in March 2014 on a flight from Kuala Lumpur to Beijing.
Mr McCormack, who serves as federal transport minister, acknowledged fresh searches may one day be launched if new technologies emerge.
"But it looks as though this will remain a mystery for the time being," he said.
Mr McCormack doubts Australia will take part in any new search efforts "at this stage".
"We've got to remember the actual plane is about 60 metres long - that's about four times less than the Titanic - which they took more than 70 years to find knowing exactly the co-ordinates of where it went down," he said.
"This is a very deep ocean, this is a large aircraft admittedly, but not that large that it was obviously easily detectable."
Mr McCormack defended the early efforts of Australian investigators, saying they were covering a massive search area based on patchy information.
"With the information they had at the time, albeit scant, they did their very best efforts."
The minister also addressed claims the Australian Transport Safety Bureau had ignored a theory in which the pilot flew the plane to the end.
"Without the black box flight recorders and all those other things, it's so difficult to know exactly what happened in the cockpit towards the end," Mr McCormack said.
"Of course, if they had the black box flight recorders they'd have the plane, but this will remain a mystery."
Malaysia signed a "no find, no fee" deal with a US company in January to resume the hunt for the plane, a year after the official search by Australia, Malaysia and China was called off.
No other search is scheduled.
Australia, Malaysia and China agreed in 2016 an official search would only resume if the three countries had credible evidence that identified a specific location for the wreckage.
