In the US, the FCC prohibits the use of cellphones in AC because this is a terrestrial based system which depends very heavily on frequency re-use. This requires that all communications are over a short distance...a few miles, typically (controlled by low power and low antennas with short line-of-sight distances). If used in an AC a cellphone has line-of-sight to many cells on the same frequency/channel and can really screw-up the cellsystem. So in addition to the obvious airborne interference issues ther are other regulatory reasons fro prohibiting such use.