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I was travelling from Mumbai to Newark Liberty Intl on United Airlines 49, a Boeing 777-200. I was sitting in the economy section, last row, last seat to the plane's left, basically, I was literally the passenger on the last seat of the aircraft.

When I sat down, I plugged my earphones into the headphone jack and I could hear the conversation between ATC and the pilot, all I had to do was just twist the and hold the jack in a certain position. I could hear them talk to Mumbai ATC, the Islamabad ATC, Kabul ATC, even up to Iceland. My question is, how is this possible? What could have happened? Did the pilot or the airline know about this? Should I have told them about this? Is it illegal to listen to this chatter? Can this happen next time I travel or was I just lucky?

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    $\begingroup$ I faintly remember on (older) airliners where they don't have an Android-based entertainment system, the remote control allows you to select audio channels. One of the channels is the plane's ATC. $\endgroup$ – kevin Mar 20 '17 at 20:30
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    $\begingroup$ I'm so jelous, Channel 9 has been disappearing on United flights for years now. It's been a long time now since I was able to listen to it. $\endgroup$ – Martin Argerami Mar 21 '17 at 1:00
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    $\begingroup$ Are you certain you heard both sides of the conversation? If you only heard the pilot, that can simply be radio-frequency-interference, the usually undesired effect of turning an audio device into an involuntary receiver for a nearby AM transmitter. Fumbling with (rusty?) connections can give you a nonlinear junction useful for demodulating AM. If you heard both sides of the conversation, though, it is more likely a service intentionally distributed in the cabin. $\endgroup$ – Paul Mar 21 '17 at 9:35
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    $\begingroup$ +1 for what Paul said. Basically anything with a diode inside of it, or an integrated circuit (since ICs have the so called body/substrate diodes) can act as a demodulator for AM. If the ratio between transmitter power and distance between the transmitter and receiver is good enough, you don't even need a specifically tuned antenna. $\endgroup$ – AndrejaKo Mar 21 '17 at 11:37
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    $\begingroup$ I remember once listening in while ATC repeatedly tried (and failed) to get the pilots of my plane to respond. They finally contacted another plane from the same airline and asked them to let our pilots know ATC was trying to talk to them through some system with the airline. I was wondering whether I should tell the flight attendants to let our pilots know that ATC wanted to talk to them... $\endgroup$ – Joel Mar 23 '17 at 15:55
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This is a feature offered on some United Airlines aircraft and flights. It's an interesting way to hear what's going on in the cockpit. You can find lots of information by searching for United channel 9.

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    $\begingroup$ It was left on channel 9 by the previous passenger. $\endgroup$ – pericynthion Mar 20 '17 at 20:40
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    $\begingroup$ And if you had to twist and hold the connector that just sounds like a bad connector. $\endgroup$ – user253751 Mar 20 '17 at 22:24
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    $\begingroup$ @Di437 There's no secrets in the communications between ATC and pilots. It's all freely broadcast, and if you have the correct equipment, you can listen in too. A easy way to do so is using the free website LiveATC (liveatc.net). It's quite neat if you're curious, or into aviation as a hobby or profession. $\endgroup$ – SnakeDoc Mar 21 '17 at 15:42
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    $\begingroup$ @Di437 If your plane from New York to Beijing is anywhere near London, the pilot is badly, badly lost. $\endgroup$ – David Richerby Mar 21 '17 at 21:56
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    $\begingroup$ @JamesMundy From the ATC recordings I've heard of pilots working emergencies, I'd be significantly calmed by being able to hear them. Pilots and ATC tend to be cool as a cucumber when things are going wrong and it's quite impressive. $\endgroup$ – ceejayoz Mar 22 '17 at 13:15
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ATC and aircraft communications (at least in the US) are not restricted for receiving. Anyone can purchase (or make) an "Air band" receiver (or scanner radio) tunable through (roughly) 118-140 MHz and listen to ATC and aircraft communications.

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