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An Indonesian Air Force officer draws an earlier flown flight pattern in a search operation for the missing Malaysia Airlines Boeing 777 at Suwondo air base in Medan, North Sumatra, Indonesia, March 13, 2014. / Binsar Bakkara, AP

Planes typically relay maintenance information in flight to their manufacturers or airlines. This data can also help track a lost plane like Air France Flight 447, which crashed in the Atlantic in 2009.

But as authorities from 12 countries continue searching for Malaysia Airlines Flight 370, government and airline officials deny a Wall Street Journal report Thursday that the plane, fueled for a five-hour flight to Beijing, actually flew for hours after last contact, based on automated signals from the plane.

Boeing, which manufactured the 777-200ER, declined to comment and Rolls-Royce, which made the engines, didn't respond to requests for comment about the plane.

But Malaysia Transport Minister Hishammuddin Hussein dismissed the Journal report as "inaccurate" and insisted the plane sent no signals after 1:07 a.m. Saturday - about 40 minutes after it took off - when air-traffic control lost contact with it.

However, Hishammuddin also said, "we have not ruled out the possibility that it has flown on."

Malaysia Airlines CEO Ahmad Jauhari said that he had contacted Boeing and Rolls-Royce, and that they "did not receive any further transmission beyond the transmission that was received at 1:07."

The technology at issue is called ACARS, for Aircraft Communications Addressing and Reporting System. The system sends different sorts of information between the plane and airlines and manufacturers on the ground. Depending on the sophistication of the information, the airline might receive the information itself or rely on the manufacturer to relay it for a fee.

John Hansman, director of the International Center for Air Transportation at Massachusetts Institute of Technology, estimates 90% of U.S. planes have some version of the system because it saves airlines money.

At first, the precise monitoring of when brakes were engaged or when planes took off or landed helped airlines track personnel costs more accurately, Hansman said. Maintenance reports can show when an engine is running hotter than usual, which signals wear, he said.

"The reason why people do this is because if something breaks in flight, if maintenance gets the message they can actually be at the landing point with the replacement part and fix the airplane and turn it around quickly," Hansman said.

In general, the messages can be sent cheaply over land by VHF signal, Hansman said. Or they can be sent over water by satellite, which is a more expensive service to send messages, he said.

The sophistication of the service depends on what the airline would like to spend. For example, Boeing promotes a service called custom alerting and analysis, which is available for 777, 747 and 787 aircraft with high-speed Internet connections. It monitors fuel, flight controls, landing gear, hydraulic power and communications.

"The major carriers collect it themselves because they have the capability of processing it and deciphering it and so forth," said David Greenberg, who worked 27 years at Delta Air Lines and is now an airline consultant as president of Compass Group. "My understanding is that Malaysia doesn't subscribe to the Boeing program and that they collect the data for their own use."

While Malaysia Airlines and its manufacturers aren't saying what sort of service was used on Flight 370, the Airbus A330 in the Air France crash had sophisticated messaging that reported problems with airspeed and altitude that helped track down the missing plane.

"In Air France, that's how they knew where to look," Hansman said.



Copyright 2014 USATODAY.com

Read the original story: Plane technology helps track missing aircraft

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