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The painstaking underwater search for Malaysia Airlines flight MH370 ended Tuesday after nearly three years — without finding a single trace of the plane.

Crews finished scouring a 46,000-square mile patch of the remote southern Indian Ocean, completing the most complex and expensive search in aviation history while also prolonging one of its greatest mysteries.

Relatives greeted the news with dismay and appealed to authorities to extend the search. "Commercial planes cannot just be allowed to disappear without a trace," said Voice370, the official association for families of missing passengers and crew.

The Boeing 777 vanished March 8, 2014 with 239 people on board while on route from Kuala Lumpur to Beijing.

Several fragments of debris have washed up on the shores of eastern Africa, but efforts to locate the main wreckage, and the black box data recorders, have failed.

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The three countries funding the ocean search — Australia, Malaysia and China — agreed last year to suspend it once the current search zone was exhausted, unless new evidence emerges that pinpoints the specific location of wreckage.

"Today the last search vessel has left the underwater search area," the MH370 Tripartite Joint Communique said in a statement.

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"Despite every effort using the best science available, cutting edge technology, as well as modelling and advice from highly skilled professionals who are the best in their field, unfortunately, the search has not been able to locate the aircraft. Accordingly, the underwater search for MH370 has been suspended."

The statement lauded the commitment of searchers in the face of what called an "unprecedented challenge."

Officials called the suspension of the search significant "for our three countries, but more importantly for the family and friends of those on board the aircraft."

"We again take this opportunity to honor the memory of those who have lost their lives and acknowledge the enormous loss felt by their loved ones," the statement said.

Australia's Transportation Safety Bureau announced in December that a review of the data used to estimate where the plane crashed, coupled with new information on ocean currents, strongly suggested the plane hit the water in a 9,700-square mile area directly north of the search zone.

However, Australia's government rejected a recommendation from the bureau that crews be allowed to search the new area to the north, saying the results of the experts' analysis weren't precise enough to justify continuing the hunt.

Voice370 said extending the search to the new area "is an inescapable duty owed to the flying public in the interest of aviation safety."

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"Having already searched [46,000 square miles], stopping at this stage is nothing short of irresponsible and betrays a shocking lack of faith in the data, tools and recommendations of an array of official experts assembled by the authorities themselves," it said in a statement.

It also appealed to the aviation industry "and the flying public across the world" to lobby the three countries to extend the search.

An interim accident report in 2014 concluded that MH370 flew off course then into a slow left turn and spiraled into the Indian Ocean when its fuel ran out.