This was apparently discerned from analysis of radar tracks from Malaysian air force air-defense radars.
That may be why the Malaysians previously announced the search area had been extended far to the west.
In a statement, Malaysia Airlines said search and rescue teams "have expanded the scope beyond the flight path to the West Peninsula of Malaysia at the Straits of Malacca." An earlier statement had said the western coast of Malaysia was "now the focus," but the airline subsequently said that phrase was an oversight.
"The search is on both sides," Civil aviation chief Azharuddin Abdul Rahman said, adding that the previous statement didn't mean that the plane was more like [sic] to be off the western coast.If the prior search areas were hundreds of miles away from where the jet went down (if it really did go down) that would certainly explain why no trace has been found.
Update: The Telegraph: "Malaysia Airlines live: military says last tracked plane hundreds of miles off course"
(Reuters) - Malaysia's military believes a jetliner missing for almost four days turned and flew hundreds of kilometers to the west after it last made contact with civilian air traffic control off the country's east coast, a senior officer told Reuters on Tuesday.
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, told Reuters.One way or another, this aircraft was hijacked. No expert am I, I admit, but I cannot imagine a navigation-system failure that would both cause this flight path and result in no attempt of the flight crew to contact ground controllers.
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.
This deviation was done by the crew on purpose, but whether under duress or on their own accord is impossible to answer at this time.
But perhaps the plane was not so much hijacked (at least in the conventional sense) as hacked:
The integrated network configurations in the Boeing Model 777-200, -300, and -300ER series airplanes may enable increased connectivity with external network sources and will have more interconnected networks and systems, such as passenger entertainment and information services than previous airplane models. This may enable the exploitation of network security vulnerabilities and increased risks potentially resulting in unsafe conditions for the airplanes and occupants. This potential exploitation of security vulnerabilities may result in intentional or unintentional destruction, disruption, degradation, or exploitation of data and systems critical to the safety and maintenance of the airplane.Federal Register, 11/18/2013, "Special Conditions: Boeing Model 777-200, -300, and -300ER Series Airplanes; Aircraft Electronic System Security Protection From Unauthorized Internal Access"