(CNN) — Investigators got new information that may help them narrow the possible whereabouts of Malaysia Airlines Flight 370 on Thursday as new details shed light on the doomed flight’s final moments early on March 8 as it flew from Kuala Lumpur toward Beijing.
A search plane has detected a possible signal — the fifth so far — from the locator beacons from the missing jet’s so-called black boxes, the Australian agency coordinating the search announced.
“The acoustic data will require further analysis overnight, but shows potential of being from a man-made source,” said retired Air Chief Marshal Angus Houston, the agency’s chief coordinator.
A senior Malaysian government official and another source involved in the investigation divulged Thursday a number of details about the flight:
• Malaysian air force search aircraft were scrambled around 8 a.m., 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.
• MH370’s pilot, Capt. Zaharie Ahmad Shah, was the last person on the jet to speak to air traffic controllers, telling them “Good night, Malaysian three-seven-zero,” Malaysian sources told CNN. 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.
• Malaysia Airlines Flight 370 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 U.S. 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 pressurization 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.