Missing Malaysia Airlines flight MH370 was "thrown around like a fighter jet" just after it vanished, in a bid to avoid radar detection, Malaysian investigators believe.
The plane, which was en route from Kuala Lampar to Beijing, is believed to have climbed to 45,000 feet – 10,000 feet higher than its normal altitude – and plummeted to just below 5,000 feet.
Speaking to the Sunday Times, a source claimed: "It was being flown very low at very high speed. And it was being flown to avoid radar."
Reports in the Malaysian newspaper the New Straits Times claim that the plane's co-pilot, Fariq Abdul Hamid, tried to use his mobile phone while the plane was in the air. This has fuelled speculation that captain Zaharie Ahmad Shah hijacked his own plane after tricking Hamid into leaving the cockpit.
However, Malaysian acting transport minister Hishammuddin Hussein has denied the claims, and said: "If this did happen, we would have known about it earlier."
However the Sunday Times sources believe it is the first proof that someone was alive on board the plane as it diverted from its planned course and flew back over the west coast of Malaysia.
"If it's true it would lead to the possibility that the pilot shut the co-pilot out of the cabin - asked him to go for coffee and then promptly locked the door - and then took over the plane.
"The co-pilot, unable to gain access, may have tried to use his mobile phone to alert the authorities," said the source.