“It’s possible to track an aircraft without a transponder with just raw radar, but it’s much more difficult,” Spencer said.
And if an airplane flew too low to be picked up by radar, controllers wouldn’t have any information about the flight, Spencer added.
Aimer said modern airplanes like the 777 also have maintenance and engine monitoring systems that keep track of such things as engine temperature and can send messages back to the airline’s base.
A U.S. official said Friday in Washington that investigators are examining the possibility of “human intervention” in the plane’s disappearance. The official, who wasn’t authorized to talk to the media and spoke on condition of anonymity, said the transponder stopped about a dozen minutes before the messaging system on the jet quit. Such a gap would be unlikely in the case of an in-flight catastrophe.
Malaysia Airlines didn’t subscribe to that messaging service, but the plane still had the capability to connect with the satellite and was automatically sending signals, or pings, the official said.
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