An official says the deep sea hunt for the missing Malaysia Airlines jetliner will likely include cutting-edge sonar when it ramps up again in October after the stormy southern hemisphere winter has passed.

The Australian Transport Safety Bureau, which is overseeing the search on Malaysia's behalf, has been criticized by some salvage experts for not choosing the advanced sonar system from the outset of the search for Flight 370 that began far off the west Australian coast last October.

The bureau said Wednesday that negotiations are underway to hire the advanced sonar equipment to add to a fourth ship that would join the search, with the aim of combing the entire 120,000-square kilometer (46,000-square mile) search area in the Indian Ocean by the middle of next year.