(ASIA NEWS NETWORK/THE STAR) The Royal Malaysian Air Force (RMAF) scrambled a search aircraft at around 8am, soon after Malaysia Airlines reported that its plane was missing, Malaysian sources told CNN.
The aircraft took off before authorities corroborated data indicating that the plane turned back westward, a senior Malaysian government official told CNN.
But the air force did not inform the Department of Civil Aviation or search and rescue operations until three days later, March 11, a source involved in the investigation told CNN.
CNN also learnt that MH370's pilot, Captain Zaharie Ahmad Shah, was the last person on the jet to speak to air traffic controllers, telling them "Good night, Malaysian three-seven-zero."
The sources said there was nothing unusual about his voice, which betrayed no indication that he was under stress.
One of the sources, an official involved in the investigation, told CNN that police played the recording to five other Malaysia Airlines pilots who knew the pilot and co-pilot.
"There were no third-party voices," the source said.
Flight MH370 disappeared from military radar for about 120 nautical miles after it crossed back over the Malaysian Peninsula, sources say. Based on available data, this means the plane must have dipped in altitude to between 4,000 and 5,000 feet, a senior Malaysian government official and a source involved in the investigation tell CNN.
The dip could have been programmed into the computers controlling the plane as an emergency maneuver, said aviation expert David Soucie.
"The real issue here is it looks like - more and more - somebody in the cockpit was directing this plane and directing it away from land," said CNN aviation analyst and former National Transportation Safety Board Managing Director Peter Goelz.
"And it looks as though they were doing it to avoid any kind of detection."
But former US Department of Transportation Inspector General Mary Schiavo was not convinced.
She said the reported dip could have occurred in response to a loss of pressure, to reach a level where pressurisation was not needed and those aboard the plane would have been able to breathe without oxygen, or to get out of the way of commercial traffic, which typically flies at higher altitudes.
That would have been necessary had the plane's transponder been turned off and it lost communications. "If you don't have any communications, you need to get out of other traffic," Ms Schiavo said.
"We still don't have any motive and any evidence of a crime yet," she said, adding that most radar can track planes at altitudes below 4,000 feet, so the plane's descent may not have indicated any attempt for whoever was controlling it to hide.
She held out hope that the black boxes hold the answers and that they will be found soon.
Flight MH370, carrying 227 passengers and 12 crew, left the KL International Airport at 12.41am and disappeared from radar screens about an hour later, while over the South China Sea. It was to have arrived in Beijing at 6.30am on the same day.
A multinational search was mounted for the aircraft, first in the South China Sea and then, after it was learned that the plane had veered off course, along two corridors - the northern corridor stretching from the border of Kazakhstan and Turkmenistan to northern Thailand and the southern corridor, from Indonesia to the southern Indian Ocean.
Following analysis of satellite data, it was concluded that MH370 flew along the southern corridor and that its last position was in the middle of the Indian Ocean, west of Perth.
Prime Minister Datuk Seri Najib Tun Razak announced on March 24, 17 days after the disappearance of the aircraft, that Flight MH370 "ended in the southern Indian Ocean".
The search continues there.