intercom + gsm

John S wrote:
wrote:

According to a Lightspeed note, it says the "FCC only allows the use
of a cell phone within the cockpit when the plane is on the ground".

This pertains to USA / FCC regulations only:

Under FCC Part 22 regulations, which describes "cellular" phones in the
850-900 Mhz band, using a Part 22 "cellular" phone while airborne is legally
prohibited.

PCS phones (e.g. T-Mobile) operate under other frequencies (e.g. 1900 Mhz band)
and are regulated under FCC Part 24. Part 24 has no prohibition against using
PCS services while airborne.

14 CFR 91.21 doesn't have that distinction....