Does the FAA prohibit cell phone use in private aircraft, or is that just an
FCC rule?

It's an FCC rule, designed to avoid overloading the old style analog
cell sites. The rule is thought not to apply to the newer digital
cell service (but I don't think it's been tested in court).

The FAA rule for part 135 ops (135.144) essentially lets the operator
of the aircraft determine what they will allow and disallow. They
make a determination that a device will or will not interfere (but
then if they determine wrong, and an accident occurs, the "careless
and reckless" clause will certainly be trotted out). I don't think
there is an equivalent rule for part 91 ops; the pilot is responsible
for the safety of the flight, which by default includes portable
electronic devices.

Jose
--
Freedom. It seemed like a good idea at the time.
for Email, make the obvious change in the address.