Although there have been no signs yet of the Malaysian airliner that remains missing far off the Australian coast, authorities are inviting expressions of interest from salvage operators in case it is found.

The Australian Transport Safety Bureau, which is coordinating the 10-month-old search, said Thursday 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 600 meters (2,000 feet) to 6.5 kilometers (4 miles) deep.

So far, the search has covered a quarter of the 60,000-square-kilometer (23,000-square-mile) search area in the Indian Ocean.