You can't answer the phone by plane. How to send?

I play hide-and-seek in the cloud. Don't expose my position.

Why can't I answer the phone by plane? The mobile phone not only sends out electromagnetic signals when dialing or answering, but also keeps in touch with the ground base station when waiting for the plane. Although the signal transmission time is short, it has strong continuity. When the plane flies smoothly, it is 6000m to12000m above the ground. At this time, the mobile phone can't receive the signal at all and can't be used. It is possible for mobile phones to get in touch with ground base stations during takeoff and landing, but the consequences of interfering with navigation systems are the most serious at this time.