Australia said it held out hope Malaysia Airlines Flight 370 would one day be found as the last search of the seabed in the remote Indian Ocean where it was believed to have been lost was scheduled to end on Tuesday.
Malaysia said last week the search by Texas-based company Ocean Infinity would end on Tuesday after two extensions of the original 90-day time limit.
Australian Transport Minister Michael McCormack said the four-year search had been the largest in aviation history and tested the limits of technology and the capacity of experts and people at sea.
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"Our thoughts are with the families and loved ones of the 239 people on board MH370," McCormack's office said in a statement. "We will always remain hopeful that one day the aircraft will be located."
Malaysia signed a "no cure, no fee" deal with Ocean Infinity in January to resume the hunt for the plane, a year after the official search in the southern Indian Ocean by Australia, Malaysia and China was called off. No other search is scheduled.
Australia, Malaysia and China agreed in 2016 that an official search would only resume if the three countries had credible evidence that identified a specific location for the wreckage.
Malaysia said last week an Ocean Infinity ship Seabed Contractor operating underwater sonar drones had searched more than 96,000 square kilometers (37,000 square miles) of sea. The search area deemed by experts to be the most likely crash site was only 25,000 square kilometers (9,650 square miles), roughly the size of Vermont.
Ocean Infinity did not immediately reply to a request for comment.
The Boeing 777 vanished on March 8, 2014, while flying from Kuala Lumpur, Malaysia, to Beijing. The original search focused on the South China Sea before analysis revealed the plane had made an unexpected turn west and then south.
Australia coordinated an official search on Malaysia's behalf that scoured 120,000 square kilometers (46,000 square miles) and cost 200 million Australian dollars ($150 million) before it ended last year.
Danica Weeks, an Australian resident who lost her husband on Flight 370, urged Foreign Minister Julie Bishop to call on the new Malaysian government to be more transparent about what they knew about the mysterious disappearance.
"There've been so many theories and rumors and ... we don't know what is true and what isn't," Weeks told Australian Broadcasting Corp.
"I want Julie Bishop to say to the Malaysian counterparts now: what do you have? Where is the investigation at?" she added.
The director of the official seabed hunt that ended last year, Peter Foley, told an Australian Senate committee hearing last week that he still hoped that Ocean Infinity would be successful.
"If they're not, of course, that would be a great sadness for all of us," Foley said.