Malaysia's Prime Minister Najib Razak (L) and Australia's Prime Minister Tony Abbott participate in a briefing on the search for Malaysia Airlines flight MH370 at RAAF Base Pearce near Perth, April 3, 2014.
An expanded team of surveillance planes and ships is scanning a vast and remote section of the southern Indian Ocean for the wreckage of Malaysia Airlines Flight 370.
Australia's Joint Agency Coordination Center, which is leading the search, said up to 10 military planes, four civil jets and nine ships are involved in the multinational effort Friday.
No trace of the plane has been found, nearly four weeks after it vanished. Officials continue to try to narrow the search area, which currently stands at a staggeringly large 217,000 square kilometers.
The Search for Flight MH370
1/10The Bluefin 21, the Artemis autonomous underwater vehicle (AUV), is hoisted back on board the Australian Defence Vessel Ocean Shield after a successful buoyancy test in the southern Indian Ocean as part of the continuing search for the missing Malaysia Airlines plane, April 4, 2014.
2/10Flight Lieutenant Stephen Graham monitors a TAC station onboard a Royal New Zealand Air Force P3 Orion during search operations for wreckage and debris of missing Malaysia Airlines Flight MH370 in the southern Indian Ocean, near the coast of Western Australia, April 4, 2014.
3/10Japan's Maritime Self-Defense Force Commander Hidetsugu Iwamasa speaks to the press in front of one of their P-3C Orion aircraft currently at RAAF Base Pearce near Perth, Australia, April 4, 2014.
4/10Relatives of Chinese passengers on board the Malaysia Airlines Flight MH370 pray in a prayer room, Beijing, China, April 4, 2014.
5/10Australia's Prime Minister Tony Abbott and Malaysia's Prime Minister Najib Razak tour RAAF Base Pearce, near Perth, April 3, 2014.
6/10Steve Wang a representative from the committee for relatives of Chinese passengers onboard Flight MH370 talks to journalists after a closed door meeting with Malaysian officials via teleconference in Beijing, April 2, 2014.
7/10An Asian elephant swims in a 65-meter-long pool at Fuji Safari Park in Susono, at the foot of Mt. Fuji, southwest of Tokyo, Japan.
8/10Koji Kubota of the Japan Coast Guard keeps watch while flying in the search zone for debris from Flight MH370, April 1, 2014.
9/10A Buddhist monk welcomes Chinese relatives of passengers on Flight MH370 as they arrive to pray at a Buddhist temple in Petaling Jaya, Malaysia, March 31, 2014.
10/10Australian Prime Minister Tony Abbott addresses the international forces currently based in Perth searching for Flight MH370 during his visit to RAAF Base Pearce, March 31, 2014.
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Authorities are desperately trying to locate the crash site before batteries run out on the plane's flight data recorder, preventing it from transmitting a radio signal. The batteries usually last about 30 days.
On Thursday, an Australian ship detected what was initially thought to be a possible signal from the so-called black box. But it was later discounted as a false alert, possibly from a sea animal or interference from shipping noise.
The international search team said it remains committed to finding the wreckage, but officials have in recent days conceded that the mystery may never be completely solved.
The jetliner vanished without any distress calls on March 8 during a flight from Kuala Lumpur to Beijing. Officials have refused to rule out any possibilities, including hijacking, sabotage, or a mechanical malfunction.
Malaysian officials have ruled out foul play from any of the plane's 239 passengers, but continue to investigate the pilots and crew for possible wrongdoing.
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