system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it that during takeoff, you are not supposed to be using laptops and phones on a flight? Does it really mess with stuff in the cockpit?
gpt
Your cell phone is not going to make a plane crash.  Trust me, we put a lot of work into these things.

What you might do is cause some noise on some of the communication lines, if a bunch of people are all doing it at once.  You're not going to kill anything, but when the pilot keeps having to ask the tower to repeat what they said, that means you having your phone on is delaying flights and driving up the cost of air travel and possibly making some people miss their flights and get stuck somewhere overnight when that couple minutes per flight adds up considering the number of flights sent out of an airport in an hour.

When you're at altitude, not a problem.  When you're in airplane mode, great.  But if you're actively using the device when the pilot would need to be in communication with the tower, not fantastic.