The search area for flight MH370 is to be extended.

The search for Malaysia Airlines MH370 will be doubled to 120,000 square kilometres and take an additional 12 months if the plane is not found in the current high priority search area of the southern Indian Ocean.

Australia, Malaysia and China agreed to extend the search, the costliest ever in world aviation, during a meeting in Kuala Lumpur on Thursday.

Australia's Transport Minister Warren Truss and his counterparts said the 120,000 square kilometres of one the world's most remote locations would cover the entire highest probability area identified by expert analysis of the plane's disappearance.

They said an additional 12 months would be needed to cover the area from May, when the current search of 60,000 square kilometres is expected to be completed, citing likely adverse weather conditions.

The ministers also agreed on plans to secure and recover wreckage if the plane is found.

Mr Truss said a priority would be recovery of the plane's black box data recorders and other parts of the aircraft relevant to the investigation.

"Then obviously if there are bodily remains and issues from the families and so forth, we'll take all of that into account in looking at what arrangements should be put in place," Mr Truss said.

Four ships have searched more than 37,000 square kilometres of the southern Indian Ocean west of Perth since last year, the equivalent of 61 percent of a designated search area.

The Boeing 777 disappeared while flying across the South China Sea from Kuala Lumpur to Beijing in the early hours of March 8 2014.

A 12-month investigation conducted by a seven-nation team of experts into the disappearance failed to uncover the cause of the disappearance and raised serious doubts over whether any of the pilots or crew hijacked the plane carrying 239 people.

No wreckage has been found in one of the world's greatest aviation mysteries.

The search area is based on expert analysis of signals or "handshakes" between an Inmarsat geostationary satellite and the plane as it flew thousands of kilometres from its flight path.

The search has been hampered by wild weather, the remote location and depths of more than 6,000 metres.

The additional search will be funded by Australia and Malaysia but efforts would be made to seek compensation from insurance Malaysia had covering the plane, the ministers said.

The search so far has cost Australia more than $100 million and Malaysia about $60 million.

Theories splashed in headlines around the world include that the plane was taken on a suicide mission, a catastrophic mechanical failure occurred and that it was accidentally shot down during a military exercise.

Mr Truss met in Kuala Lumpur with Malaysia's Transport Minister Liow Tiong Lai and China's Transport Minister Yang Chuantang.

More than 150 of the passengers on board the plane were from China.