Searchers for Malaysia Airlines flight MH370 are still trying to narrow the search area before deploying an undersea drone to help find it.
But there have been no confirmed acoustic detections from the plane’s black boxes in the past 24 hours amid fears the batteries are fading.
Up to 11 military aircraft, one civil aircraft and 14 ships on Sunday will search an area of up to 57,506 square kilometres, about 2200km northwest of Perth, where it is believed the plane crashed after mysteriously vanishing en route from Kuala Lumpur to Beijing with 239 people on board on March 8.
Australian Defence Vessel Ocean Shield is continuing focused sweeps with a towed pinger locator to try to locate further signals, supported by British ship HMS Echo.
Military AP-3C Orions are continuing their acoustic search of the area.
“This work continues in an effort to narrow the underwater search area for when the Autonomous Underwater Vehicle is deployed,” the Joint Agency Co-ordination Centre said in a statement.
“There have been no confirmed acoustic detections over the past 24 hours.”
The weather forecast for Sunday is south easterly winds with isolated showers, sea swells up to one metre and visibility of five kilometres in showers.
Prime Minister Tony Abbott on Saturday said pings from the surface search area have helped authorities narrow down the over-sea area.
But fears remain the black box batteries will run out.
“The object of all this is to get as much transmission as we can from the fast-fading black box recorder,” he said.
“When we think we’ve got everything we can through this means, we will deploy a submersible. By that stage we hope we will have narrowed the search area on the sea bed to as little perhaps as a square kilometre.”
He said success wasn’t certain, and if it was it might still take weeks or months.
“There’s a lot of difficulty and a lot of uncertainty left in this,” Mr Abbott said.
“It is the most difficult search in human history and no one should underestimate the challenges involved in finding wreckage four and a half kilometres below the surface of the ocean.”
Meanwhile, the co-pilot of the missing airliner MH370 might have attempted to make a mid-flight call from his mobile phone just before the plane vanished from radar screens.
The call ended abruptly possibly “because the aircraft was fast moving away from the (telecommunications) tower”, The New Straits Times quoted a source as saying.
But the Malaysian daily also quoted another source saying that while Fariq Abdul Hamid’s “line was reattached”, there was no certainty that a call was made from the Boeing 777 that vanished on March 8.
The report – titled a “desperate call for help” – did not say who he was trying to contact.
Fariq and Captain Zaharie Ahmad Shah have come under intense scrutiny after the plane vanished.