Why satellites didn't find missing plane »

Cars have Global Positioning System devices to pinpoint where drivers are when they get lost, so why can't GPS be used to locate the exact position of planes when the worst happens?

It took search and rescue teams over 30 hours to locate the wreckage of the Air France plane that crashed in the Atlantic on Monday. The aircraft's onboard GPS system was no help to rescuers in the mission.

Although details of Flight 447's fate remain uncertain, in some air accidents, this critical time could mean the difference between life and death for any survivors.

Michel Roelandt, aviation expert for Eurocontrol, a European air navigation safety organization, told CNN that some planes are fitted with GPS systems, but these are essentially "dumb" units -- like those in cars -- that receive location information from satellites but do not send any data back.
So while a flight crew knows its exact position over an ocean, the information is not automatically sent to air traffic control. That is left to someone in the cockpit to relay via satellite communication when the plane is out of radar range. According to industry experts, satellite technology that would allow constant monitoring of an aircraft's exact position is available, and although plans are afoot to introduce it, cost may be deterring some airlines.

"Airlines often have a contract with a private operator to provide their satellite communications. Some companies pay for it, some have free contracts," Roelandt said.

The United States owns most of the GPS satellites in space that track the positions of commercial aircraft. As long as an airplane is within range of two to three satellites in space, it uses them to triangulate its position and send the information to the nearest ground station via a transponder, said Bill Waldock, professor of safety science at Embry Riddle University in Prescott, Florida.

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