Every time you hop on a plane, you hear some sort of announcement about shutting off your cell phone or putting it into airplane mode.

Maybe you listen, if you haven't already conked out in your seat. Or maybe you ignore the rule and keep texting, hoping the flight attendant won't notice. I mean, what's the risk? Will your extra game of Words with Friends really bring down the plane?

Well it could, at least in theory. The concern is that portable electronic devices like your phone or tablet could cause electromagnetic interference that would disrupt the communication or navigational systems in the plane.

One type of interference, known as Front Door interference, is when radio waves leak out windows or other cracks in the metal frame, and are detected by the antennas on the outside of the plane. Those antennas are used to communicate with air traffic controllers or with GPS satellites, so it could make it more difficult to send and receive those important messages. There's also Back Door interference, were radio waves interfere with the signals running through the cables inside the plane, which could scramble on board electronic systems.

But since the 1980s, electrical systems on aircraft have been able to withstand lightning and other sources of electromagnetic disturbance, which probably shields them from the tiny amount of interference from the phone or tablet. And no phone, tablet, or any gadget you might try to use during a flight has ever actually been proven to cause serious problems.

Individual pilots have claimed that some of their instruments went haywire when passengers turned on certain devices, but it's tough to show cause and effect. Most of the time when investigators try to recreate the problem, nothing happened. So while some interference is possible, it doesn't seem to happen much, and certainly isn't causing huge problems that jeopardize planes.

But there's another reason why cell phones and their full non-airplane mode glory are banned in flight. Back in 1991, when cellphones were basically giant bricks, The Federal Communications Commission, or FCC, was worried about phones on planes clogging up cell signals for people on the ground. Phones up in the air might be close to a bunch of cell towers at once, confusing the system.

Plus, because the airplane is moving super fast, the phones will be trying to connect to tower after tower, taking up precious bandwidth. It turns out that doesn't really happen, though, because again, planes these days have all that shielding. So having your phone transmitting probably won't bring down the plane or clogged up cell networks, but you might as well follow the rules; you're not going to get much cell service up there anyway.

Thanks for asking, and thanks for spending your time on the internet with me, learning about science. If you wanna learn more about planes in particular, check out "Why Does Plane Food Taste So Bad?" where I explained to you why you should drink tomato juice on your next flight.