Australia's prime minister yesterday announced an expanded search across a huge swathe of seabed where flight MH370 might have crashed seven weeks ago, admitting it was now "highly unlikely" that any surface wreckage would be found.
The hunt for the Boeing 777 in the southern Indian Ocean has so far yielded nothing on the surface or below, baffling authorities who are struggling to explain the loss of the aircraft.
"I regret to say that thus far, none of our efforts in the air, on the surface, or undersea have found any wreckage," Prime Minister Tony Abbott said.
"It is highly unlikely at this stage that we will find any aircraft debris on the ocean surface," he added, noting that a surface area of more than 4.5 million square kilometres had been scanned. "By this stage, 52 days into the search, most material would have become water-logged and sunk," Abbott said.
The Malaysia Airlines flight disappeared on March 8 carrying 239 people - mostly Chinese - and is believed to have crashed in the southern Indian Ocean after mysteriously diverting from its Kuala Lumpur to Beijing journey.
Abbott said the search would now enter a new phase involving undersea efforts being ramped up. He said the new search area, which spans 700 kilometres by 80 kilometres, could take from six to eight months to completely examine.
The search zone has been defined by analysis of satellite data, and was boosted by several detections of transmissions believed to have come from the plane's black box recorders before their batteries died.
A submersible Bluefin-21 scouring a 400-square-kilometre zone centred around one of these transmissions had failed to yield results.
Abbott said the Australian government, in consultation with Malaysian authorities, was willing to engage one or more commercial companies to undertake the work. He estimated it would cost A$60 million (HK$432 million).
Until now, the eight nations involved in the Indian Ocean search - Australia, New Zealand, Malaysia, Japan, Korea, the United States, Britain and China - had been bearing their own costs. Abbott said Canberra would ask for help in funding the next stage.
"We will be seeking some appropriate contribution from other nations involved, but we will ensure that this search goes ahead," he said.
Australia is working closely with Malaysia and China. Beijing said it would actively support the next phase as it also called for international support.
Steven Wang, whose mother was on the plane, said that by expanding the underwater search area Australian authorities had suggested they were not sure they were searching in the right place.
"If they could find out what happened to the plane maybe they could find the plane more easily," he said.
"But they just search the whole ocean, and it is such a big ocean, and you cannot search everywhere. It will take years."