A key detail in the investigation into the disappearance of a Malaysia Airlines plane has been thrown into doubt, with the the airline's chief saying it is now not clear when the plane's tracking system was turned off.
Flight MH370 with 239 people on board vanished about an hour after it took off from Kuala Lumpur to Beijing early on 8 March. An unprecedented search has failed to find any trace of the Boeing 777, which investigators believe was diverted by someone with deep knowledge of the plane and commercial navigation.
Uncertainty over exactly when the satellite data system on the missing Malaysia Air jet, flown by Captain Zaharie Ahmad Shah and co-pilot Fariq Abdul Hamid, stopped transmitting has revived speculation the flight suffered a major mechanical or electronic problem that could recur in similar aircraft.
Malaysia Airlines now says it believes that the co-pilot signed off "all right, goodnight" - the last radio transmission two minutes before the plane's transponder, which relays radar information on the plane's location, stopped working and 16 minutes before its next satellite data transmission was due to be sent, CNN reports.
The former inspector-general of America's transportation department, Mary Schiavo, says any problem with the plane needs to be resolved because many other planes of that model are used by airlines.
The new timeline means the plane may have actually been hit by a mechanical malfunction, CNN reports. This could be very significant, because the revision means that the communications systems, which the media were led to believe were switched off before the unconventional sign-off, may have been still working.
The person saying 'goodnight' could have been in charge of a plane that was working totally normally, and whatever happened occurred after that. That raises the possibility that it was a catastrophic mechanical failure, rather than a deliberate human act.
However, the New York Times reported on Monday the turn that diverted the missing plane off its flight path was programmed into the aircraft's computer navigation system, probably by someone in the cockpit.
Rather than manually operating the plane's controls, whoever altered Flight 370's path typed seven or eight keystrokes into a computer situated between the captain and the co-pilot, US officials said.
The computer is called the Flight Management System. It directs the plane from point to point specified in the flight plan submitted before a flight. It's not clear whether the plane's path was reprogrammed before or after it took off.
A veteran US pilot believes investigators are right to look at the possibility of equipment failure as well as speculation over terrorism and hijacking scenarios. Les Abend, a Boeing 777 captain and writer for Flying magazine, said it's possible there was a problem serious enough for the crew to have lost control of the plane before a distress signal was sent. Though major electrical and electronic failures are rare, they could prevent critical information from being transmitted, he said.
China searching its territory, Australia scales back area
China on Tuesday began searching for the missing jet in the part of its own territory inside a northern corridor through which it, theoretically, could have flown.
Satellite data suggests that the plane could be anywhere in either of two vast arcs: one stretching from northern Thailand to the borders of Kazakhstan and Turkmenistan, or a southern arc from Indonesia into the Indian Ocean west of Australia.
China and Kazakhstan are searching in the northern corridor from Laos to the Caspian Sea, while Australia and Indonesia are leading the search from the west of Sumatra to the south of the Indian Ocean. Twenty-six countries have been asked for help.
China's ambassador to Malaysia said on Tuesday there is no evidence that Chinese passengers - who made up half the plane's manifest - were involved in a hijack or terror attack on the flight, the BBC reports.
One theory put forward several days ago is that the plane might have flown in a north-western arc, which would include almost 3000km of Chinese territory. There are few other details regarding China's search, but it is likely it will be conducted by its military.
Meanwhile, Australia's maritime safety agency said on Tuesday it has sharply reduced its search for the jetliner to a 600,000 square kilometre corridor in the southern Indian Ocean. However, that is still roughly the size of Spain and Portugal combined.
The Australian Maritime Safety Authority said the search field had been narrowed from 19 million square kilometres, based on analysis of satellite data collected from the plane by the US National Transportation Safety Board, Reuters reports. AMSA had streamlined that data further to account for water movements in the days since the plane disappeared.
The US said it is withdrawing one of its naval ships and is sending and a surveillance plane to Western Australia. The Poseidon long-range aircraft will be based with New Zealand's Orion and Australian Air Force planes north of Perth.