Canberra: The missing Malaysia Airlines jet appears to have been on autopilot as it flew south across the Indian Ocean until running out of fuel, and the likeliest scenario is that the crew of Flight 370 was unresponsive, possibly suffering from the effects of oxygen deprivation, Australian officials said on Thursday in announcing a new deep-sea search for the aircraft.

A report issued by the Australian Transport Safety Bureau, outlining how the new search zone had been chosen, said the most likely scenario as the Boeing 777-200 headed south across the Indian Ocean on March 8 was that the crew was suffering from hypoxia or was unresponsive for another reason.

Hypoxia occurs when a plane loses air pressure and the pilots, lacking adequate oxygen, become confused and incapable of performing even basic manual tasks.

Evidence for an unresponsive crew as the plane flew south includes the loss of radio communications, a long period with no manoeuvring of the aircraft, a steadily maintained cruise altitude and eventual fuel exhaustion and descent, the report said.