There are two sides to this: EMC is black magic and airplane safety is another and thus nobody is willing to say that using random RF devices onboard of plane

There are two sides to this: EMC is black magic and airplane safety is another and thus nobody is willing to say that using random RF devices onboard of plane is safe - for one reason it's almost impossible to test. By the way owner's manual for my new car contains paragraph that explicitly disallows usage of any RF transmitter inside the car that does not have external antenna (and I would assume that most car manufacturers include similar paragraph in their manuals and also that everybody ignores them). Cellular networks and cell phones are not designed for relative speeds and RF propagation modes of high flying commercial aircraft. Most access methods of digital wireless networks depend on precise timing where propagation delays are significant and thus need to compensate for relative movement of phone and base station and there are pretty low limits of how fast movement can be compensated (it's almost practical to drive car faster than speed limit of GSM1800). Also higher levels of cellular protocol stacks are not exactly prepared for situation when phone sees large number of accessible cells with quite strong signal and this set changes very quickly.