Urban legend - even in NMT days, the antennas on cell towers were directional and tried to avoid uselessly radiating upwards. Good luck getting usable signal at

Urban legend - even in NMT days, the antennas on cell towers were directional and tried to avoid uselessly radiating upwards. Good luck getting usable signal at any flight level of commercial flight. Even if you're low enough, it's not uncommon for calls to drop due to speed (in fact a common problem on higher speed trains, and newer cell networks do include improvements for high speed terminals due to that). The mobile phone is just the most common device that is required to have its transmitter shut down, and part of that is that what is fine for home/office environment is not fine in aviation environment (different regulatory domains et al) so the easiest way is to mandate shutting down all transmitters then whitelist certain kinds (2.4GHz stuff like Bluetooth tends to get a pass because 2.4GHz is unlicensed due to possible interference from airliner's microwave ovens)