KUALA LUMPUR, Malaysia -- A Malaysia Airlines plane sent signals to a satellite for four hours after the aircraft went missing, an indication that it was still flying for hundreds of miles or more, a U.S. official briefed on the search said Thursday.
Six days after the plane with 239 people aboard disappeared, Malaysian authorities expanded their search westward toward India, saying the aircraft may have flown for several hours after its last contact with the ground shortly after takeoff from Kuala Lumpur for Beijing.
A string of previous clues about Flight MH370 have led nowhere.
"This situation is unprecedented. MH370 went completely silent over the open ocean," acting Malaysian Transport Minister Hishammuddin Hussein said. "This is a crisis situation. It is a very complex operation, and it is not obviously easy. We are devoting all our energies to the task at hand."
The U.S. official, who spoke on condition of anonymity because he wasn't authorized to discuss it by name, said the Boeing 777-200 wasn't transmitting data to the satellite, but instead sent out a signal to establish contact. Boeing offers a satellite service that can receive a stream of data during flight on how the aircraft is functioning and relay the data to the plane's home base. It provides information before the jet lands on whether maintenance work or repairs are needed.
Malaysia Airlines didn't subscribe to the service, but the jet still had the capability to link with the satellite and automatically send pings, the official said.
"It's like when your cell phone is off, but it still sends out a little 'I'm here' message to the cell phone network," the official said. "That's how sometimes they can triangulate your position, even though you're not calling, because the phone every so often sends out a little bleep. That's sort of what this thing was doing."
The jet had fuel to fly about four more hours, the U.S. official said. Boeing didn't comment.
Messages involving a different, more rudimentary data service also were received from the airliner for a short time after the plane's transponder -- a device used to identify the plane to radar -- went silent, the official said.
If the jet had disintegrated in flight or suffered some other catastrophic failure, all signals -- the pings to the satellite, data messages and transponder -- would be expected to stop too.
One part of the hunt is in the South China Sea, where the aircraft was seen on civilian radar flying northeast before vanishing without any indication of technical problems. A similar-sized search is also being conducted in the Strait of Malacca because of military radar sightings that might indicate the jet turned in that direction after its last contact, passing over the Malay Peninsula. The search area being covered is about 35,800 square miles, the size of Portugal.
Asked if it were possible that the plane kept flying for several hours, Mr. Hishammuddin said: "Of course. We can't rule anything out. This is why we have extended the search. We are expanding our search into the Andaman Sea." The sea is northwest of the Malay Peninsula.
He said Malaysia was asking for radar data from India and other neighboring nations to see if they can trace it flying northwest. India says its navy, air force and coast guard will search in the south Andaman Sea.
"Because of new information, we may be part of an effort to open a new search area in the Indian Ocean," White House spokesman Jay Carney said earlier Thursday, declining to offer details about that information or the new area. The U.S. Navy 7th Fleet said it is moving one of its ships, the USS Kidd, into the Strait of Malacca, west of Malaysia.
In the latest disappointment, search planes failed to find jet debris after being sent Thursday to a South China Sea area off Vietnam's southern tip, where satellite images on a Chinese government website reportedly showed three suspected floating objects. "There is nothing." Mr. Hishammuddin said.