The Boeing 777-200 wasn't transmitting data to the satellite, but was instead sending out a signal to establish contact, said the official, who spoke on condition of anonymity because he wasn't authorized to discuss the situation by name.
Boeing offers a satellite service that can receive a stream of data during flight on how the aircraft is functioning and relay the information to the plane's home base. The idea is to provide information on whether maintenance work or repairs are needed before the plane lands so mechanics and parts can be ready, saving time and money.
Malaysia Airlines didn't subscribe to that service, but the plane still had the capability of connecting with the satellite and was automatically sending pings, the official said.
"It's like when your cellphone is off but it still sends out a little 'I'm here' message to the cellphone 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 continuing pings led searchers to believe the plane could have flown hundreds of miles or more beyond its last confirmed sighting on radar, the official said. The plane had enough fuel to fly about four more hours, he said.
The plane was en route from Kuala Lumpur to Beijing when radar contact was lost. 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.
The plane was initially thought to have gone down over the South China Sea. According to defence officials, the USS Kidd, a destroyer, is heading into the Indian Ocean. A U.S. surveillance plane is in the Strait of Malacca region and another U.S. surveillance plane is now en route to Malaysia, defence officials said.
Associated Press writers Lolita C. Baldor in Washington and Scott Mayerowitz in New York contributed to this report.
Follow Joan Lowy on Twitter at http://www.twitter.com/AP_Joan_LowySuggest a correction