They tested the cellphone thing on Mythbusters.
The reason cellphones aren't allowed on planes during takeoff or landing is because, though there's no known cases of cellphones intefering with avionics, it would be too expensive and nearly impossible to test all combinations of phones and avionics equipment to allow them to give a definitive answer. So they do it just to be on the safe side.
The reason cellphones aren't allowed on planes during takeoff or landing is because, though there's no known cases of cellphones intefering with avionics, it would be too expensive and nearly impossible to test all combinations of phones and avionics equipment to allow them to give a definitive answer. So they do it just to be on the safe side.