The international team hunting Malaysia Airlines Flight MH370 in the remote southern Indian Ocean failed to turn up anything on Friday, and Australia's deputy prime minister said the suspected debris may have sunk.
Aircraft and ships have also renewed a search in the Andaman Sea between India and Thailand, going over areas that have already been exhaustively swept to find some clue to unlock one of the biggest mysteries in modern aviation.
(Read more: MH370: Objects sighted near Australia are 'credible')
This handout Satellite image made available by the AMSA (Australian Maritime Safety Authority) shows a map of the areas searched between March 18 and March 20, 2014 for missing Malaysian Airlines Flight MH370.Getty Images
The Boeing 777 went missing almost two weeks ago off the Malaysian coast with 239 people aboard. There has been no confirmedsign of wreckage but two objects seen floating deep south in the Indian Ocean were considered a credible lead and set off a huge hunt on Thursday.
Australian authorities said the first aircraft to sweep treacherous seas on Friday about 2,500 km (1,500 miles) southwest of Perth was on its way back to base without spotting the objects picked out by satellite images five days ago.
"Something that was floating on the sea that long ago may no longer be floating," Deputy Prime Minister Warren Truss told reporters in Perth. "It may have slipped to the bottom."
But the search was continuing and Australian, New Zealand and U.S. aircraft would be joined by Chinese and Japanese planes over the weekend.
"It's about the most inaccessible spot that you can imagine on the face of the Earth, but if there is anything down there, we will find it," Australian Prime Minister Tony Abbott told reporters in Papua New Guinea, where he is on a visit.