Everyone who has traveled by plane know the drill: before taking off, switching your phone to airplane mode is a must.
But has anyone bothered asking why?
Maybe it's because either we're still too sleepy or excited before the flight that no one even thought of asking the flight stewardess why cellphones have to be turned off during the entire travel time.
All that's left are a few hunches such as the fact that maybe the signal couldn't reach a high altitude anyway, or your network provider is out of reach, or the your phone might disrupt aircraft systems. You get the picture.
Before your imagination goes as far as a crash, though, the answer to the question is actually simple.
Your phone needs to be in airplane mode during the flight because your device's signals can cause radio interference that could be quite annoying for pilots, especially when they're communicating with the ground officials in an airport.
Here is the sound that we're talking about:
Now, imagine a hundred passengers whose phones are all on normal mode. How much annoying phone signal sounds will the pilots and ground technicians be able to pick up on their radios? That's quite a lot of unnecessary noise which will disrupt the communication necessary for air traffic instructions.
Some claim that mobile phone signals interfere with the aircrafts' navigation performance. However, there's not enough proof that it can cause an aircraft malfunction. Just to be safe though, pilots are not taking any chances by instructing every passenger to switch their devices to airplane mode. After all, it's better to be safe than sorry.