The search for the missing Malaysia Airlines plane now encompasses an area stretching 7.7 million square kilometres, larger than the entire land mass of Australia.
An unprecedented search operation involving 26 nations has failed to find any trace of flight MH370, which went missing 11 days ago with 239 passengers on board, including six Australians.
Investigators believe it was diverted by someone with deep knowledge of the Boeing 777-200ER and commercial navigation, and flown perhaps thousands of kilometres off its scheduled course from Kuala Lumpur to Beijing.
"The entire search area is now 2.24 million square nautical miles (7.7 million square kilometres)," Malaysia's acting transport minister Hishammuddin Hussein said in a daily press briefing.
"This is an enormous search area."
Australia has a land mass of about 7.6 million square kilometres.
Investigators believe the plane could have been flown in one of two different directions after its tracking systems were turned off - either north-west into Asia or south-west into the Indian Ocean.
Australia is in charge of the southern Indian Ocean search, which began in an area 3,000 kilometres south-west of Perth early yesterday.
The Australian Maritime Safety Authority (AMSA) says the southern search zone covers 600,000 square kilometres of ocean and has been plotted using data based on the last satellite relay signals sent by the plane.
Australia, New Zealand and US search southern corridor
Aircraft and ships from Australia, New Zealand and the United States are taking part in that search, which represents a narrowing down of the previous Indian Ocean search area.
The size of the search zone mirrors the second area the same distance from the equator in the northern hemisphere.
The southern search currently includes three P-3 Orion aircraft provided by the Royal Australian Air Force, with a fourth to be made available tomorrow.
A New Zealand P-3 Orion and a US P-8 Poseidon are expected to join the search today.
One merchant vessel is also searching the area with a further two vessels due to help out.
AMSA's emergency response general manager, John Young, says the search area will be assessed daily.
"We will be moving the search area according to the movement of water and weather influences every day," he said.
"When the aircraft actually get out there and see the real conditions and get experience with the search we will modify our thinking, but at the moment it's a large area with aircraft that are towards the end of their operating limit.
"So they get a short period of time in the search area and that dictates it's going to take quite a long time."
Mr Young says "a needle in a haystack remains a good analogy" and that the search could be ongoing for weeks.
"We are taking this search very seriously. I am describing it as a possibility. The aircraft could have gone north or south," he said.
"Our purpose is firstly to find anyone alive if there is anyone to be found [and] secondly, to prove or discount the possibility that the aircraft came south - to do that would be a significant development in the search."
China has begun searching for the missing jet in its own territory in the possible northern flight corridor, the country's state media said, citing Beijing's envoy in Kuala Lumpur, Huang Huikang.
State media also quoted Mr Huang as saying no evidence had been found linking the 153 Chinese passengers aboard the missing flight to terrorism or hijacking.
Motive remains unclear as Chinese families threaten hunger strike
Police and intelligence agencies have yet to establish a clear motive to explain the plane's disappearance.
Intensive background checks of everyone aboard have so far failed to find anyone with a known political or criminal motive to hijack or deliberately crash the plane.
Investigators piecing together patchy data from military radar and satellites believe someone turned off the aircraft's identifying transponder and ACARS system, which transmits maintenance data, and turned west, re-crossing the Malay Peninsula and following a commercial aviation route towards India.
Malaysian officials have backtracked on the exact sequence of events - they are now unsure whether the ACARS system was shut down before or after the last radio message was heard from the cockpit - but say that does not make a material difference.
Factbox: AP-3C Orion

- Used for maritime surveillance, search-and-rescue operations and anti-submarine warfare
- Range: Up to 15 hours
- Maximum speed: 750 kilometres per hour
- Crew: Pilot, co-pilot, 2 flight engineers, tactical commander, navigator/communicator, up to 6 sensor operators
- Capacity: Air-sea rescue kit, survival aid heliboxes, sonobuoys, maritime marker devices
- Wingspan: 30.8 metres
- Can fly up to 35,000 feet
(Source: RAAF)
"This does not change our belief, as stated, that up until the point at which it left military primary radar coverage, the aircraft's movements were consistent with deliberate action by someone on the plane," Mr Hishammuddin said.
"That remains the position of the investigating team."
Authorities remain under pressure from desperate relatives of Chinese passengers who have threatened to go on a hunger strike in protest against the lack of information on the search.
Two-thirds of the passengers on the flight were Chinese.
Outside a gathering of families of missing passengers, a woman clutching a placard reading "Respect life. Give us back our families" told reporters the relatives were going on a hunger strike.
"Since they haven't given us the truth about those people's lives, all of us are protesting," the woman said.
"All the relatives are facing mental breakdowns."
Wen Wancheng, whose son was on board the missing flight, said some of the relatives had stopped going to the meetings, given how long they had been waiting for information.
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Chinese relatives of passengers from the missing Malaysia Airlines flight MH370 wait for news at a hotel in Beijing on March 17, 2014. (AFP: Mark Ralston)
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Fariq Abdul Hamid was the co-pilot who uttered the words "all right, good night" before Malaysia Airlines flight MH370 went missing en route from Kuala Lumpur to Beijing.
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A man leaves a message of support and hope for passengers of the missing Malaysia Airlines MH370 at the Kuala Lumpur International Airport on March 15, 2014. (Reuters: Damir Sagolj )
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A pilot on board a Vietnamese Air Force Russian-made AN-27 uses a map to help search Vietnam's southern sea for missing Malaysia Airlines flight MH370 on March 14, 2014. (AFP: Hoang Dinh Nam)
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Indonesian Air Force pilot aboard an Indonesian Air Force military surveillance aircraft over the Malacca Strait searches for the missing plane on March 13, 2014. (AFP: Indonesian Air Force)
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A sand sculpture in support of the missing Malaysian airliner MH370, by artist Sudersan Pattnaik, sits on a beach at Puri Beach in India on March 12, 2014. (AFP)
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Photo showing what was originally thought to be possible debris from the missing Malaysia Airlines flight MH370 floating in the South China Sea, March 12, 2014. Several satellite photos were released on the website of a Chinese state oceanic agency, but were released "by mistake and did not show any debris". (www.sastind.gov.cn/)
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Photo showing what was originally thought to be possible debris from the missing Malaysia Airlines flight MH370 floating in the South China Sea, March 12, 2014. Several satellite photos were released on the website of a Chinese state oceanic agency, but were released "by mistake and did not show any debris". (www.sastind.gov.cn/)
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A Vietnamese officer stands next to a screen showing a flight route during a press conference about the search for a missing Malaysian airliner, at Phu Quoc Airport. (Reuters)
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An RAAF crew member in an AP-3C Orion patrol plane looks out a window and scans the surface of the sea west of Peninsula Malaysia during the search for Malysian Airlines flight MH370 on March 11, 2014. (ADF: Cameron Jamieson)
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A Vietnamese official checks a map during a search flight off Vietnam's coast on March 11, 2014 as part of continued efforts aimed at finding traces of the missing Malaysia Airlines MH370. (AFP: Hoang Dinh Nam)
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Malaysian police photographs showing 19-year-old Iranian Pouria Nour Mohammad Mehrdad (L) and an unidentified man (R), who both boarded missing Malaysia Airlines MH370 flight using stolen European passports. The images were displayed to the media on March 11, 2014 (AFP: Malaysian Police)
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Malaysian officials stand in front of a map showing the extended search area for missing flight MH370, March 10, 2013. (How Foo Yeen/Getty Images)
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Personnel from the Republic of Singapore Air Force scan the seas north-east of Kota Baru, Malaysia, for any signs of the missing plane. (AFP: The Strait Times/Desmond Lim)
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An officer looks out of a helicopter during a mission to find the missing plane. (Reuters: Athit Perawongmetha)
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Graphic of the flight path for Malaysia Airlines flight MH370 that last had contact with air traffic controllers on March 8, 2014. (ABC News)
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A Vietnamese Air Force officer looks out a window of a Soviet-made AN-26 during the search for the missing Malaysia Airlines plane over seas south off Vietnam. (AFP: Hoang Dinh Nam)
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Journalists wait for a news conference regarding the missing Malaysian Airlines flight at a hotel in Beijing. (Reuters: Jason Lee)
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Malaysia Airlines Group chief executive Ahmad Jauhari Yahya addresses the media near Kuala Lumpur International Airport. (AFP: Manan Vatsyayana)
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A man takes pictures of a flight information board displaying the scheduled time of arrival of flight MH370 at the Beijing Capital International Airport. (Reuters: Kim Kyung-Hoon)
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A woman believed to be the relative of a passenger onboard flight MH370 cries as she talks on her mobile phone at the Beijing Capital International Airport. (Reuters: Kim Kyung-Hoon)
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A relative (C) of a passenger onboard Malaysia Airlines flight MH370 covers her face at Beijing Capital International Airport. (Reuters: Kim Kyung-Hoon)
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The second RAAF P-3C Orion on the tarmac in Darwin ready to depart for Malaysia to join the search party on March 10, 2014. (ABC News: Marty McCarthy)
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New Zealand father-of-two, Paul Weeks, who was on board missing Malaysia Airlines flight MH370. (ABC TV)
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Rodney and Mary Burrows were among the six Australians on board the missing Malaysia Airlines flight. (Queensland Police Service)
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Queenslanders Catherine and Robert Lawton, pictured on holidays. (Facebook)
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Malaysia Airlines plane missing
ABC/wires