Flight MH370, carrying 239 passengers and crew, disappeared from radar screens on March 8 shortly after taking off from Kuala Lumpur bound for Beijing.
Investigators say what little evidence they have to work with, including the loss of communications, suggests the Boeing 777 was deliberately diverted thousands of kilometers from its scheduled route.
The search was narrowed last month after a series of acoustic pings thought to be from the plane’s black box recorders were heard near where analysis of satellite data put its last location, some 1,000 miles (1,600 km) off the northwest coast of Australia.
“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 agency in charge of the search said in a statement.
ATSB chief Martin Dolan told Reuters he expected the team to take two to three weeks to reassess and re-analyze the data, although he was “confident” that the final resting place of the aircraft was the Indian Ocean.
“We don’t know what those pings were,” Dolan said over the phone. “We are still analyzing those signals to understand them better.”
The discovery of the pings on April 5 and 8 was hailed as a significant breakthrough, with Australian Prime Minister Tony Abbott expressing confidence that searchers knew where the plane wreckage was within a few kilometers.
However, a thorough scan of the 850 sq km area around the pings with an unmanned submarine failed to find any sign of wreckage. No debris linked to the plane has been picked up despite the most extensive and expensive search effort in aviation history.
“We concentrated the search in that area because the pings were the best information available at the time,” Australian Deputy Prime Minister Warren Truss, who is also the transport minister, told the Australian parliament.
“We are still very confident that the resting place of the aircraft is in the southern [Indian] Ocean, and along the seventh ping line,” he added, referring to an arc identified by analysis of satellite communications data from UK company Inmarsat Plc.
Earlier on Thursday, CNN quoted Michael Dean, the US Navy’s deputy director of ocean engineering, and said authorities now almost universally believe the pings did not come from the plane’s onboard data or cockpit voice recorders.
“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,” Dean told CNN.
The search zone had already been extended to a 60,000 sq km zone that is being surveyed by a Chinese vessel. It will then be searched by a commercial operator in a mission that is expected to start in August and take up to a year, at a cost of 60 million Australian dollars (55 million US dollars) or more.
Malaysia’s government and Inmarsat released data this week used to determine the path of MH370, which families of the missing passengers hope could help verify the plane’s last location by opening up the data to analysis by a wider range of experts.
Australian authorities said the data supported the theory that the plane crashed after running out of fuel.
Along with surface searches, examination of satellite data and the undersea sonar searches, authorities have asked the United Nations’ Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) to check its system of hydrophones, designed to pick up possible nuclear tests, for any clues as to where the aircraft may have crashed.
“Both the CTBTO and institutions from our 183 Member States…have analyzed all relevant International Monitoring System data—infrasound, seismic and hydroacoustic—without finding any signal that could point to the fate of MH370,” a spokesman from CTBTO said in an emailed response.