Why can't you use phones on planes?
Because phones can fall out of the window.
No.
It might be because portable electronic devices like cell phones and tablets emit radio signals.
These signals can interfere with the flight controls.
They may also disrupt the communication with the air traffic controllers on the ground.
Besides this, cellular towers are miles below the airplane.
Hence, cell phones try to emit a stronger radio signal to detect the network.
This can increase the possibility of causing interference with the airplane electronic equipment.
Really.
I didn't know that.
Hence, portable electronic devices are told to be either turned off or to be kept on airplane mode or flight mode.
This prevents the emission of radio signals, thus helping to keep all the onboard equipment working properly.