Missing plane search intensifies as second signal detected

Australian co-ordinators in the search for a missing Malaysian plane say a Chinese ship has detected a pulse signal for a second time, within hours of it being heard earlier on Saturday.

Air Chief Marshal Angus Houston called the discovery in the southern Indian Ocean an "important and encouraging lead".

He warned that the data were still unverified.

British naval ship HMS Echo is sailing to the area to investigate further.

It is expected to arrive in the early hours of Monday.

Australian aircraft were also on their way, Air Chief Marshal Houston told reporters. Australian naval vessel Ocean Shield would be heading to the latest search area once it had investigated a third acoustic detection elsewhere.

Both HMS Echo and ADV Ocean Shield have technology able to detect underwater signals emitted by data recorders.

Malaysia Airlines flight MH370 disappeared on 8 March with 239 people on board. Investigators believe it crashed in the Indian Ocean although no confirmed debris has been found. The battery-powered signal from the "black box" recorders fades after 30 days.

A multinational team is desperately trying to find debris floating in the water or faint sound signals from the data recorders that could lead them to the missing plane and unravel the mystery of its fate.

Finding floating wreckage is key to narrowing the search area, as officials can then use data on currents to backtrack to where the plane hit the water, and where the flight recorders may be.

Beacons in the black boxes emit "pings" so they can be more easily found, but the batteries last for only about a month.

Officials have said the hunt for the wreckage is among the hardest ever undertaken, and will get much harder still if the beacons fall silent before they are found.

"Where we're at right now, four weeks since this plane disappeared, we're much, much closer,'' said aviation expert Geoffrey Thomas, editor-in-chief of AirlineRatings.com.

"But frustratingly, we're still miles away from finding it. We need to find some piece of debris on the water; we need to pick up the ping.''

If it doesn't happen, the only hope for finding the plane may be a full survey of the Indian Ocean floor, an operation that would take years and an enormous international operation.