The Malaysian authorities have confirmed that the plane disappeared from the air traffic control screens after flying for 1 hr and 10 mts, after taking off from Kuala Lumpur.
Flying at an altitude of 35,000 feet, the airliner was midway between Malaysia's east coast town of Kota Bharu and the southern tip of Vietnam.
"It changed course after Kota Bharu and took a lower altitude. It made it into the Malacca Strait," said investigators.
Air force chief Rodzali Daud confirmed that the military radar detected the plane at 2:40 amon Saturday, close to the island of Pulau Perak at the northern end of the Strait of Malacca. It was spotted flying at a height of 9,000 metres.
However, the report is being checked by the Department of Civil Aviation and the search and the rescue team.
Assuming that the plane's transponder and tracking devices were switched off, it would have maintained a cruising altitude of 500 km. Malaysia, thereafter has shifted its focus to the Malacca Strait, after focusing on the South China Sea.