PERTH (AFP) - The hunt for underwater signals from missing Flight MH370 is likely to continue for days before a robot submersible is deployed to comb the seabed, the Australian search chief said on Tuesday.
"We need to continue that (search) for several days to the point at which there is absolutely no doubt that the pinger batteries will have expired," Mr Angus Houston said.
"Until we stop the pinger search we will not deploy the submersible."
Describing sonic "pings" picked up by the naval vessel Ocean Shield as the "most promising lead" so far, Mr Houston said at a press briefing: "There is still some doubt. But I'm more optimistic than I was one week ago."
Speaking at the same news conference, Australian Defence Minister David Johnston thanked all nations involved in the search, calling the multi-nation cooperation "absolutely first class".
Up to eleven military planes, three civilian planes and 14 ships are taking part on Tuesday in the unprecedented search 2,200 kilometres northwest of Perth.
The apparent signals breakthrough came as the clock ticks past the 30-day lifespan of the emergency beacons of the two data recorders from the Malaysia Airlines jet, which vanished on March 8 with 239 people on board en route from Kuala Lumpur to Beijing.