Planes, ships and state-of-the-art tracking equipment are hunting for any trace of the passenger jet, which Malaysia said crashed in the forbidding waters after veering far from its intended course.

They face a huge challenge locating the Boeing 777's "black box", which holds vital clues to determining what caused the plane to vanish after it took off from Kuala Lumpur en route to Beijing on March 8.

But experts believe the flight data recorder and cockpit voice recorder may not yield answers on the riddle of how and why the plane diverted an hour into the flight, and embarked on a baffling journey to the southern reaches of the Indian Ocean.

The data recorder details the aircraft's path and other mechanical information for the flight's duration, and "should provide a wealth of information", US-based aviation consultancy firm Leeham Co said in a commentary.

But the cockpit voice recorder, which could reveal what decisions were made by those at the helm and why, retains only the last two hours of conversations before the plane's demise.

That means potentially crucial exchanges surrounding the initial diversion, which took place halfway between Malaysia and Vietnam, will be lost.

"Clearly, it won't reveal anything that happened over the Gulf of Thailand, this will have been overwritten by the end of MH370," it said.

Leeham added that it also remains to be seen whether the cockpit recorder will contain anything pertinent about the plane's final two hours, when it is believed to have either ditched or run out of fuel.

Malaysian Prime Minister Najib Razak said on Monday that Flight MH370 had gone down in the Indian Ocean with its 239 passengers and crew, citing new satellite data analysis.

But its exact location and the circumstances of its diversion remain a mystery. No distress signal was ever received.

Three scenarios have gained particular traction: hijacking, pilot sabotage, or a sudden mid-air crisis that incapacitated flight crew and left the plane to fly on auto-pilot for several hours until it ran out of fuel.

Malaysia has said it believes the plane was deliberately diverted by someone on board.

But with the travelling public and aviation industry hanging on every twist in the drama, no firm evidence has emerged from a Malaysian investigation to support any of the theories circulating.

British aviation expert Chris Yates said that even if the black boxes are found, "it seems unlikely that we will get that answer" of why the plane ended up thousands of kilometres off course.

"We still have no idea as to the mental state of the pilot and co-pilot, we have no idea if somebody managed to get into the cockpit to seize the aircraft, and we've certainly had no admissions of responsibility since this whole episode started," he told BBC television.

"It is a mystery like no other"

Debris has been sighted far off Australia's west coast but an international search effort has been unable to retrieve any for confirmation, and wreckage could have drifted hundreds of kilometres from where the plane crashed.

"As investigators, we deal with physical evidence and right now we don't have any physical evidence to work with," Anthony Brickhouse, a member of the International Society of Air Safety Investigators, told AFP.

The batteries powering the locator signal of the black boxes will run out in less than two weeks.

A US device capable of detecting that signal even on the ocean floor was being sent to the scene, but weather and treacherous sea conditions have hampered the effort to pinpoint the black box location.

Paul Yap, an aviation lecturer at Singapore's Temasek Polytechnic, said that if the black box is not found, "chances are we are never going to find out what really happened".

"With the new satellite data, I think we can say it is a chessboard," he said of the wide search area.

"The question now is to find which grid on that chessboard to focus on, where the black boxes are."