Malaysia's military believes a jetliner missing for almost four days turned and flew hundreds of kilometres to the west after it last made contact with civilian air traffic control off the country's east coast, a senior officer said.
In one of the most baffling mysteries in recent aviation history, a massive search operation for the Malaysia Airlines Boeing 777-200ER has so far found no trace of the aircraft or the 239 passengers and crew.
Malaysian authorities have previously said flight MH370 disappeared about an hour after it took off from Kuala Lumpur for the Chinese capital Beijing.
"It changed course after Kota Bharu and took a lower altitude. It made it into the Malacca Strait," the senior military officer, who has been briefed on investigations, said.
That would appear to rule out sudden catastrophic mechanical failure, as it would mean the plane flew around 500 km (350 miles) at least after its last contact with air traffic control, although its transponder and other tracking systems were off.
A non-military source familiar with the investigations said the report was one of several theories and was being checked.