The last message from the cockpit of the missing Malaysia Airlines flight was routine. "All right, good night," was the signoff transmitted to air traffic controllers five days ago.
Then the Boeing 777 vanished as it cruised over the South China Sea toward Vietnam, and nothing has been seen or heard of the jetliner since.
Those final words were picked up by controllers and relayed Wednesday in Beijing to anguished relatives of some of the 239 people aboard Flight MH370.
The search for the missing plane, which left Kuala Lumpur for Beijing early Saturday, now encompasses 35,800 square miles (92,600 square kilometres) of Southeast Asia and is expanding toward India.
After several days of sometimes confusing and conflicting statements, the Malaysian military officially disclosed why it was searching on both sides of country: A review of military radar records showed what might have been the plane turning back and crossing westward into the Strait of Malacca.
Air force chief Gen. Rodzali Daud said the radar showed an unidentified object at 2:15 a.m. about 200 miles (320 kilometres) northwest of Penang. "I am not saying it's Flight MH370. We are still corroborating this. It was an unidentifiable plot," he said.
Foreign experts and the manufacturers of the radar were studying the images to try to determine whether the blips were in fact the missing plane. For now, authorities said the international search effort would stay focused on the South China Sea and the strait leading toward the Andaman Sea.