By Tom Westbrook
SYDNEY (Reuters) - Australia said on Wednesday it was not ruling out a future underwater search for a missing Malaysia Airlines passenger jet as families of those on board criticised the decision to suspend the hunt after three fruitless years.
The location of Flight MH370 has become one of the world's greatest aviation mysteries since the plane, a Boeing 777, disappeared in 2014 en route to Beijing from the Malaysian capital of Kuala Lumpur with 239 people on board.
"I don't rule out a future underwater search by any stretch," Australian Transport Minister Darren Chester told reporters in Melbourne, a day after Australia, Malaysia and China called off the search in the southern Indian Ocean.
The search cost about A$200 million ($150 million), mostly paid by Malaysia, and had already been extended twice. But the three countries involved have been reluctant to keep looking without new evidence about the plane's final resting place.
A recommendation from investigators last month to look to the north of the 120,000 sq km (46,000 sq mile) area that has been the focus of search efforts was rejected by Australia and Malaysia as too imprecise.
Chester said cost had not been the determining factor to halt the search, but he said restarting it would require "credible new information which leads to a specific location".
Prime Minister Malcolm Turnbull on Wednesday expressed "deep regret" that the plane had not been found, but reaffirmed the agreement between Malaysia, Australia and China to stop looking.
Boeing <BA.N> did not immediately respond to requests for comment.
Flight MH370 lost contact over the Gulf of Thailand in the early hours of March 8, 2014. Subsequent analysis of radar and satellite contacts suggested someone on board may have deliberately switched off the plane's transponder before diverting it thousands of kilometres out over the Indian Ocean.
Since the crash, there have been competing theories over whether the plane was hijacked and whether it was under the control of anyone when it finally ran out of fuel.
The head of the Australian Transport Safety Bureau (ATSB), which led the hunt, said authorities were confident it was not in the area that has been searched.
ATSB chief commissioner Greg Hood said "residual search activity", including satellite and drift analysis would continue until the end of February.
But quitting the underwater search drew a swift and angry reaction from relatives of those on board, who had called for the hunt to be expanded.
Most of the passengers were from China.
About 30 relatives of victims gathered at a monthly meeting with Malaysian Airlines officials in Beijing on Wednesday to protest against the end of the search.
Relatives told Reuters the airline invited four representatives to go to Malaysia and discuss the decision but they had rejected the offer.
Dan Shuqin, 63, whose sister was on the flight, said authorities had been "playing tricks" for three years.
"Can four family members speak for all 140 family members?" she asked.
Instead, the relatives called for Malaysian authorities to hold a meeting with the families in China.
An airline spokeswoman said its Post Accident Office was in constant contact with family members, but did not give any further details.
On Tuesday, Jiang Hui, whose mother was on board the flight, told Reuters he felt "disappointed, helpless and angry" because the search had been ended.
There was also anger on social media at the news.
"Didn't they say they would never end the search? What the hell happened?" wrote one user on China's Weibo service.
The only confirmed traces of the plane have been three pieces of debris found washed up on the island country Mauritius, the French island Reunion and an island off Tanzania.
As many as 30 other pieces of wreckage found there and on beaches in Mozambique, Tanzania and South Africa are suspected to have come from the plane.
($1 = 1.3250 Australian dollars)
(Additional reporting by Ben Blanchard in Beijing; Editing by Lincoln Feast, Robert Birsel)