Updated

Despite no firm clue to the whereabouts of a Malaysian airliner being discovered since it disappeared 10 months ago far off the Australian coast, authorities on Thursday invited expressions of interest from salvage operators in case the wreck is found.

The Australian Transport Safety Bureau, which is coordinating the search, said that expressions of interest were being sought to prepare for recovery operations in the event Malaysia Airlines Flight 370 is located.

The planning for the recovery of the Boeing 777, which vanished on March 8 with 139 people aboard, comes as four ships continue a sonar and video search of a mountainous seabed, which ranges from 2,000 feet to 4 miles deep.

So far, the search has covered a quarter of the 60,000-square-kilometer (23,000-square-mile) priority search area in the Indian Ocean, about 1,800 kilometers (1,100 miles) west of Australia. Not a single piece of debris or wreckage has been found

"While no wreckage from the missing aircraft has yet been found, preparations are being made so a recovery operation can be mobilized quickly and effectively when needed," Deputy Prime Minister Warren Truss said in a statement.

The expressions of interest would enable the bureau to assess which salvage operators have the equipment and expertise required for any recovery, he said.

Decisions on any recovery operation would be made jointly by the Australia, Malaysia and China, Truss said. Most of the passengers were Chinese.

If nothing is found, the search is expected to end in May.

The jetliner veered sharply off course during a flight from Kuala Lumpur to Beijing and flew for hours with its communications systems disabled before it is presumed to have run out of fuel.