Pooh Bear wrote:

The origin of the ban was due to concerns about cellphone transmissions
interfering with onboard avionics.

The origin of the ban on cellphone usage at altitude was to prevent phones from
hitting multiple receivers which were using the same frequency. The designers of the
AMPS system counted on being able to have many "cells" use the same frequency set
because they were far apart. Put the phone in the air, and several of these stations
would receive the transmissions from the call.

The origin of the FAA ban on electronic devices is as you say, but it is not unique
to cell phones.

George Patterson
If a man gets into a fight 3,000 miles away from home, he *had* to have
been looking for it.