Perth:
The intensive aerial search for surface wreckage from Flight MH370 officially ended on Wednesday as the hunt was drastically scaled back with ships also moving out of the remote Indian Ocean area where the plane is believed to have gone down.
Australian authorities said the focus would transition "over the coming weeks" to a more intensified undersea search in the quest to find out what happened to the Malaysia Airlines flight with 239 people aboard that disappeared on March 8.
Eight nations have been involved in the unprecedented hunt -- Australia, New Zealand, Malaysia, Japan, South Korea, the United States, Britain and China -- with more than 300 sorties flown across a vast expanse of remote ocean looking for debris.
But with nothing to show for their efforts from scanning more than 4.5 million square kilometres (1.5 million square miles) from the air since March 18, the planes have been stood down.
"Most of the aircraft will have left by the end of today," a spokesman for the Australian-led Joint Agency Coordination Centre told AFP, although an Australian P-3 Orion would remain on standby in Perth.
The United States, Japan, New Zealand and Malaysia all confirmed that their aircraft were returning to base. There was no immediate word Wednesday from China, which accounted for most of the passengers on board.
As many as 14 ships from Australia, China and Britain were also involved in scanning the ocean surface for debris or black box signals but many of these are also pulling out.
"Some need to head back to port and refuel and give the crew a rest, others will go back to doing what they were doing for their respective nations before they joined the search," the spokesman said.
"In essence, the surface search has been scaled back. We will keep a few vessels out there and others on standby, but the large-scale air and sea search has ended."
On Monday, Australian Prime Minister Tony Abbott announced the focus would shift to an expanded underwater search across a huge swathe of seabed where the plane might have crashed, admitting it was now "highly unlikely" that any surface wreckage would be found.
The US Navy submersible Bluefin-21 has been scouring a 314-square kilometre zone centred around one of the transmissions believed to have come from the plane's black box flight recorders before their batteries died.
But it too has failed to find anything with poor weather hampering efforts on Wednesday.
Abbott said an area of up to 56,000 square kilometres of the ocean floor would be scoured in the new search with the Bluefin remaining in operation along with other technology, possibly a specialised side-scan sonar.