Chinese and Australian ships have detected signals that may be from the plane’s flight recorder.
A number of pings likely from flight recorders of the missing Malaysian airlines are yet the best lead in the month-long search for the plane, head of the Australian agency coordinating the search has said.
The jet disappeared March 8 with 239 people on board.
An Australian ship connected to a U.S. Navy towed pinger locator has picked up signals with a transmitted frequency consistent with the beacons from aircraft black box recorders.
Defence vessel Ocean Shield acquired the signal twice, once for more than two hours, said Air Chief Marshal Angus Houston, who is leading the search.
A Chinese ship had earlier detected a similar signal in an area more than 300 nautical miles from the latest signals. Chinese patrol ship Haixun 01 reported receiving a pulse signal with a frequency of 37.5 kHz, consistent with the signal emitted by flight recorders, on Friday and again on Saturday.
Mr. Houston said on Monday that the signal was the most promising lead yet. But he said more information and time would be needed.
“Clearly this is a most promising lead, and probably in the search so far, it’s probably the best information that we have had,” Mr. Houston said at a news conference.
“We’ve got a visual indication on a screen and we’ve also got an audible signal — and the audible signal sounds to me just like an emergency locator beacon.”
The signal was picked up in an area some 1,680 km (1,040 miles) northwest of Perth, Australia, determined as the most likely place the plane went down.
“I’m much more optimistic than I was a week ago,” Mr. Houston said. “We are now in a very well defined search area, which hopefully will eventually yield the information that we need to say that MH370 might have entered the water just here.”
He said the Ocean Shield was still in the area but had not re-established the signal since. One the position of the signals is fixed, the Ocean Shield could lower an autonomous vehicle called the Bluefin 21 underwater to try to locate wreckage on the sea floor.
The signal had been heard in sea with a depth of 4,500m, he added, which was at the limit of the capability of the Bluefin 21.
The search for aircraft is one of the most intensive in history. Most of the passengers aboard the airplane were Chinese.
The black boxes record cockpit data and may provide answers about what happened to the Malaysia Airlines plane.