The missing Malaysia Airlines plane is not in the Indian Ocean search zone where acoustic "pings" were detected, search co-ordinators have confirmed.
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MH370: Southern Indian Ocean search concluded
Since the Bluefin-21 submarine found no remnants of missing flight MH370 in the Southern Indian Ocean search zone, the Joint Agency Co-ordination Centre said on Thursday, the area can be 'discounted as the final resting place' of the aircraft.
MH370 went missing on March 8 about one hour into a night flight from Kuala Lumpur to Beijing.
"The Australian Transport Safety Bureau [ATSB] has advised that the search in the vicinity of the acoustic detections can now be considered complete and, in its professional judgment, the area can now be discounted as the final resting place of MH370," the Joint Agency Co-ordination Centre said on Thursday.
The co-ordination centre announced on April 7 that a pinger locator towed from the Australian navy vessel Ocean Shield had picked up two acoustic signals, with one held for more than two hours.
At the time, it described the signals as consistent with flight data or cockpit voice recorders, the most promising lead yet and likely from a man-made source.
Two days later, two more signals were detected, holding for about five and seven minutes.
The signals prompted Australian Prime Minister Tony Abbott to say he was "very confident" they were from the black box of the plane that vanished en route to Beijing from Kuala Lumpur.
The JACC's statement on Thursday came hours after reports that the search had gone back to square one, citing US Navy deputy director of ocean engineering Michael Dean as saying the pings came from some other man-made source unrelated to MH370.
"Our best theory at this point is that [the pings were] likely some sound produced by the ship ... or within the electronics of the Towed Pinger Locator," he said.
However, a US Navy spokesman retorted: "Mike Dean's comments today were speculative and premature, as we continue to work with our partners to more thoroughly understand the data acquired by the towed pinger locator.
"As such, we would defer to the Australians, as the lead in the search effort, to make additional information known at the appropriate time."
JACC has also confirmed the end of the Bluefin-21 mission, with the underwater drone detecting no signs of aircraft debris since it began scanning the sea floor off the West Australian coast on April 14.
The Bluefin-21 has scoured more than 850 square kilometres of the ocean floor looking for signs of the missing aircraft, but has been constrained by depth operating limits and technical hitches.
Having earlier narrowed down the search area based on the pings, JACC is now casting its net much wider, saying it continues to review all existing radar, satellite and aircraft performance data to define a search zone of up to 60,000 square kilometres in the southern Indian Ocean.
That zone still follows an arc defined by British company Inmarsat based on the final "handshakes" between the Boeing 777 and satellites.
Relatives of the 239 passengers and crew were recently successful in calling for Inmarsat's data to be released publicly, not convinced that searchers were looking in the right place.
JACC said the findings of the data review would be made public "in due course".
And it is not only pushing ahead with sea floor mapping in the "defined" search area, it is also adding more vessels to the survey, which is expected to take about three months.
A fresh, potentially deeper underwater search will follow, beginning in August and taking up to 12 months.
A formal request for tender to undertake the search would be released soon, JACC said.
"A single prime contractor will be chosen to bring together and manage the expertise, equipment and vessels to carry out the search," it said.
A Chinese survey ship, Zhu Kezhen, is mapping areas of the sea floor in preparation for the commercially contracted deep ocean search.
Transport Minister Warren Truss has told Federal Parliament the search is about to move into a new phase and Australia was committed to doing everything it can to find the plane.
"We are still very confident that the resting place of the aircraft is in the Southern Ocean," he said.
The next stage of hunting for the plane involves an extensive review of data. The next search begins in August and is expected to take about 12 months.
"Unfortunately this is a painstaking effort in a very large ocean."
The next area could be 800 kilometres long and 70 kilometres wide, he said.
Manager of opposition business Tony Burke said the hopes of many had been dashed by the failure to find the plane in the most recent search zone.
"Once again we offer our condolences and words of comfort to the families and friends of the passengers on MH370 who still await more news," he said.