You're flying in a plane and the seatbelt sign is turned off. you're in the

You're flying in a plane and the seatbelt sign is turned off,  You're in Stratosphere
This happen when you usually entered 16km in height. Up to this point, it would be safe to use wireless communication device.

hope this helps

In my own word cell technology can  lead to advances in the understanding of diseases mechanism and transmission because diseases is very bad