"Can you help clear up the legality of using cell phones in small aircraft? " - Brian D.
“FAA Advisory Circular 91-21.1B provides us our answer:
The Federal Communications Commission (FCC) currently prohibits the use of cell phones while airborne.
Its primary concern is that a cell phone, used while airborne, would have a much greater transmitting range than a land mobile unit. Their use could result in unwanted interference to transmissions at other cell locations since the system uses the same frequency several times within a market or given operating area.
Since a cell phone is capable of operating on various cellular frequencies, unwanted interference may also affect cellular systems in adjacent markets or operating areas. The FAA supports this airborne restriction for other reasons of potential interference to aircraft systems and equipment.
Currently, the FAA does not prohibit the use of certain cell phones in aircraft while on the ground.”