In-Flight Cell Phones Need Path to Antennas
Passengers on the hijacked airliners were able to dial 911 or call relatives to say goodbye because their planes were within range of ground-based cellular network antennas.
In-flight cell phone calls are illegal because of concerns the signals could interfere with navigational equipment. Of course, that was not a concern of the desperate people who telephoned from Tuesday’s flights.
Though mobile phones are not designed for air-to-ground communication, they work if they have a direct line of sight to a cell tower.
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