The possibility of interference is negligible. NASA did a study of
several systems in several different aircraft and found worst case path
losses around -50dB. This is before the antenna gain (selectivity) and
receiver band-pass filtering are taken into account.
Boeing investigated reported incidents with extensive testing & could
not duplicate the claims in a laboratory:
http://www.boeing.com/commercial/aeromagazine/aero_10/interfere_textonly.html
Aircraft systems mostly operate in VHF and below, whereas GSM is in the
UHF band (900 Mhz and 1800 MHz). The only exception is GPS which sits at
1575 Mhz.
It's the other way around. In fact, if there *was* any interference with
flight systems then you could probably make a strong case for negligence
by the operator or manufacturer.
I have a conspiracy theory that GSM phones need to be switched off at
altitude only because up there they go nuts switching between towers. I
suspect that mobile phone use is banned for this reason.
In this context, arresting someone for endangerment to the aircraft is a
joke.
I have a feeling that the CPUs within the devices actually cause more
interference but paradoxically, pilots allow people to use PDAs in
"flight mode" (which is RF off, CPU on).
