Fading signals add urgency to search for missing jet

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Royal New Zealand Air Force Captain Flight Lieutenant Timothy McAlevey sits in the cockpit of a RNZAF P3 Orion maritime search aircraft as it flies over the southern Indian Ocean looking for debris from missing Malaysian Airlines flight MH370 April 11, 2014. Search and rescue officials in Australia are confident they know the approximate position of the black box recorders from missing Malaysia Airlines Flight MH370, Australian Prime Minister Tony Abbott said on Friday. [Photo/Agencies]

The search for a missing Malaysia Airlines jetliner resumed on Saturday, five weeks after the plane disappeared from radar screens, amid fears that batteries powering signals from the black box recorder on board were about to die.

Australian Prime Minister Tony Abbott said signals picked up during the search in the remote southern Indian Ocean, believed to be "pings" from the black box recorders, were "rapidly fading".

"While we do have a high degree of confidence that the transmissions that we've been picking up are from flight MH370's black box recorder, no one would underestimate the difficulties of the task still ahead of us," Abbott told a news conference in Beijing.

Malaysia Airlines Flight MH370 disappeared soon after taking off on March 8 from Kuala Lumpur bound for Beijing with 227 passengers and 12 crew on board, triggering a multinational search that is now focused on the Indian Ocean.

Search officials say they are confident they know the approximate position of the black box recorder, although they have determined that the latest "ping", picked up by searchers on Thursday, was not from the missing aircraft.

Batteries in the black box recorder are already past their normal 30-day life, making the search to find it on the murky sea bed all the more urgent. Once searchers are confident they have located it, they then plan to deploy a small unmanned "robot" known as an Autonomous Underwater Vehicle.

"Work continues in an effort to narrow the underwater search area for when the autonomous underwater vehicle is deployed," the Australian agency coordinating the search said on Saturday.

"There have been no confirmed acoustic detections over the past 24 hours," it said in a statement.

The black box records data from the cockpit and conversations among flight crew and may provide answers about what happened to the plane, which flew thousands of kilometres off course after taking off.

The mystery has sparked the most expensive search and rescue operation in aviation history.