My friend recently returned from a trip to China on business. He took his personal mobile phone and a company phone. He turned the phone Off that he had in his shirt pocket but left the other phone on in the locker. Of course you should comply with air regulations which is generally to turn your phone off or over to Flight mode.
When my friend landed and checked the phone, he had welcome messages from phone networks in over 5 countries that he flew over but never landed at, including the Netherlands, Swizterland, and other eastern European countries. It's proof that you can get a signal, whilst moving at 500mph at 35000ft!
