"We're throwing everything we have at this search,'' Australian Prime Minister Tony Abbott told Nine network television on Wednesday.
"This is about the most inaccessible spot imaginable. It's thousands of kilometers from anywhere,'' he later told Seven Network television. He vowed that "we will do what we can to solve this riddle.''
Watch: MH370: Suspected flight path
In Beijing, some families held out a glimmer of hope their loved ones might somehow have survived. About two-thirds of the missing are Chinese, and their relatives have lashed out at Malaysia for essentially declaring their family members dead without any physical evidence of the plane's remains. Many also believe that the Malaysian officials have not been transparent or swift in communicating information with them about the status of the search.
Wang Chunjiang, whose brother was on the plane, said he felt "very conflicted.''
"We want to know the truth, but we are afraid the debris of the plane should be found,'' he said while waiting at a hotel near the Beijing airport for a meeting with Malaysian officials. "If they find debris, then our last hope would be dashed. We will not have even the slightest hope.''
In China's capital a day earlier, nearly 100 relatives and their supporters marched to the Malaysian Embassy, where they threw plastic water bottles, tried to rush the gate and shouted, "Tell the truth! Return our relatives!''
In a statement of support for the families, Chinese President Xi Jinping ordered a special envoy to Kuala Lumpur to deal with the case, and Deputy Foreign Minister Xie Hangsheng told Malaysia's ambassador that China wanted to know exactly what led to the announcement that the plane had been lost, a statement on the ministry's website said.
The plane's bizarre disappearance March 8 shortly after it took off from Kuala Lumpur en route to Beijing has proven to be one of the biggest mysteries in aviation.
Investigators will be looking at various possibilities, including mechanical or electrical failure, hijacking, sabotage, terrorism or issues related to the mental health of the pilots or someone else on board.
MH370 relatives protest at Malaysian embassy
The search for the wreckage and the plane's flight data and cockpit voice recorders could take years because the ocean can extend to up to 7000 metres deep in some parts.
It took two years to find the black box from an Air France jet that went down in the Atlantic Ocean on a flight from Rio de Janeiro to Paris in 2009, and searchers knew within days where the crash site was.
There is a race against the clock to find Flight 370`s black boxes, whose battery-powered "pinger'' could stop sending signals within two weeks. The batteries are designed to last at least a month.
David Ferreira, an oceanographer at the University of Reading in Britain, said little is known about the detailed topography of the seabed where the plane is believed to have crashed.
"We know much more about the surface of the moon than we do about the ocean floor in that part of the Indian Ocean,'' Ferreira said.
The Australian Maritime Safety Authority, which is coordinating the southern search operation Malaysia's behalf, said the focus Wednesday will be on an 80,000 square kilometre swathe of ocean. Ships and aircraft are looking for possible debris that has drifted from the suspected crash zone. The area is about 2000 kilometres southwest of Perth.
Various pieces of floating objects have been spotted by planes and satellite, but none have been retrieved or identified.
Australia's Bureau of Meteorology warned that weather was expected to deteriorate again Thursday with a cold front passing through the search area that bring rain thunderstorms, low clouds and strong winds.
Malaysia announced Monday that a complex analysis of satellite data by foreign experts had concluded that flight had ended in a remote corner of the Indian Ocean, far from any landing strip.
The conclusions were based on an analysis of the brief signals the plane sent every hour to a satellite belonging to Inmarsat, a British company, even after other communication systems on the jetliner shut down for unknown reasons.
The airline's chairman, Mohammed Nor Mohammed Yusof, warned it may take a long time for further answers to become clear.
"The investigation still underway may yet prove to be even longer and more complex than it has been since March 8th,'' he said.
- AP
