Lv 6
_ asked in Cars & TransportationAircraft · 1 decade ago

Why did mobile phones work on airplanes in the US on 11Sept01?

Why did mobile phones work over NY and Pennsylvania on 11Sept01, the anniversary date of the end of the last Arab crusade of Europe, and not before or since? Technology for mobile phone use on planes is new and still being tested as the signal must be retransmitted, boosted, to reach a ground station. So why did they work there on that day and not on other days?

10 Answers

  • 1 decade ago
    Favorite Answer

    I can't believe some of the answers given here. Has anyone ever left their phone on during a flight? They do not work, plain and simple. If I'm flying my own airplane I must fly a few thousand feet above the ground and be near a town or highway to pick up any signal. While cell towers have a long range, they are designed to reach horizontally, not vertically.

    Next time in an airliner, leave your cell phone on. Watch the signal, you will loose all signal within 10 minutes and won't see any signal again until you are about to land. The FCC requires all phones to be off because phones are not tso'd (technical service order), or approved for use on an airplane. It is extremely expensive to receive a tso, and each and every cell phone would have to receive a tso for the FAA to allow phones to be used on planes. Its too much work to verify each phone carried by each passenger and allow some and not others to be turned on. In reality, cell phones are not going to cause any interference to navigation, so leave your phone next time and see what happens.

    The phone calls made from airplanes on 9/11 were not made from cell phones, they were made from airphones in the backs of the seats on larger airliners.

  • 4 years ago

    They do affect the aircraft systems, mainly the ILS (Instrument Landing System). This system receives signals from the airfield telling them whether their approach is good or not. The frequencies used in this system are very close, if not identical to Mobile phone signals. I have seen an experiment in which a mobile phone was set to transmit (call somebody) and at the same moment the vertical bar on the display (see diagram on second link) showed full deflection right (telling the pilot to steer hard right whilst landing!) In bad weather/night, this could prove fatal for all of the passengers and crew!

  • 1 decade ago

    Cell phones do work in airplanes they did before sep11 and after. the reason they tell you to turn off your phone is in fact because in the air they work TOO GOOD.

    True, there is a threat of minor interference with delicate instruments used to control and navigate the plane, and this is most crucial at takeoff and landing. That's why they ask you to turn off ALL electronics for take off and landing. However once you're airborne you are told "It's now safe to use your approved electronics"... But why is it that you then can turn on everything but your phone?

    On the ground cell phones communicate with cell towers. At any given time your phone may be in reach of several towers. Those towers must then communicate with each other in order to sort out which tower will transmit your calls. now take your phone up to 30-40 thousand feet, suddenly your phone is in reach of possibly hundreds of towers. Consider this and then remember that your plane with 90 people on board is not the only flight. with this potential logistics nightmare the FCC extends is regulatory powers to the skys and outlaws the use of cell phones on commercial flights.

    Remember 40,000 feet is roughly 7 1/2 miles, cell towers are often further apart then that, so don't believe any one who says a cell signal can't reach the ground.

    "While cell towers have a long range, they are designed to reach horizontally, not vertically."

    Thats pretty logical... so why not just lean it over on it's side?

  • Anonymous
    1 decade ago

    It's not that mobile phones don't work on planes, the airlines don't permit the use of such phones in flight. Mobile phones do work on planes in flight, assuming the plane is close enough to the ground. However, the signals from the phone may interfere with the electronics on the plane and are therefore not permitted. Of course, on 9/11, rules were of secondary importance.

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  • 1 decade ago

    cell phones will always work on airplanes. Airlines just dont permit the use of them due to the POSSIBLE interference with the navigation and communications equipment on aircraft.

    on 9/11 however, everyone was paying attention to the hijackings of the aircraft and no one was paying any particular attention to the rules and regulations at that time.

  • 6 years ago

    Cell phone use is banned on commercial aircraft. They tried

    to legalize it but failed due to safety reasons and the noise

    it would cause. (Who would want to sit next to someone in

    a two hour conversation with someone on the ground, anyway)

    Now, we need to pass a federal law banning all cell phone use

    while driving. This is a danger to everyone on the road. If you

    must make a call, pull over and stop, then make the call. You

    may just save a life that way and it could be your own.

  • 1 decade ago

    its not that phones cant work aboard planes, they can depending on the altitude, its just that they MAY interfere with the navigation systems. What they are testing now is a way for it not to interfere with the aircraft avionics.

  • Anonymous
    1 decade ago

    My knowledge is that the phones on the a/c were satilite phone and would work at any flight level. Cell phones generally quit after 10k feet and up.

    Source(s): A&P Mech
  • Anonymous
    1 decade ago

    1) the planes were close to the ground, they were not 25,000 feet up.

    2) I guess that people figure it was better to ask forgiveness rather than permission at the time.

  • jtexas
    Lv 7
    1 decade ago

    they weren't really concerned with navigation interference.

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