micaoct

As a fast method to shut off the radio on your phone. Most people use it to save battery power in low signal areas.

Civilian aircraft use VHF for both navigation radios and communication. (30 MHz to 300 MHz is the range for VHF). Navigation radios use 108 to 117.95 and air communication is 118-137 MHz. Phones operate on UHF, 900/1,800/1,900 MHz.

The FCC (speaking from a US perspective) has these separated for a reason. I assure you, using your phone on a civilian aircraft will have no adverse effects. However, always listen to your cabin crew, because that is legally binding, if they tell you to turn your stuff off, turn it off; it is an FAA/EASA rule, and you have to adhere to it. However, if your seatmate has their phone out, don't worry, it won't crash the plane.

It has nothing to do with messing with the "electronics". It is all about making sure people aren't playing with their phones during the safety briefing and also ensuring that in the contingency that something happens, those phones/iPads/laptops/etc that people are holding aren't going to be deadly projectiles. Avionics are not affected.