Most GPS receivers are receive-only. Seems that some use very low power transmitters to clean up/convert signals, but those are seriously weak. A decent number of airlines already allow them.

The issue may be that there's a difference between "GPS" which is technically a strictly-receiver service (your phone never talks to the satellites, only maybe mumbles to itself) and "Location Services" that frequently mixes GPS with cell-based location estimates (which are at least trying to actively talk to cell towers).