There still must be cells providing signal. On a couple of occasions I've forgotten to turn of my (Sprint 3G) phone. When I've looked at it before turning it off, there was no signal whatsoever- not even enough for a time synch...searching... This was at altitude, probably near final cruising altitude.

So, even if the experiment does work out ok, will it really be possible, in most cases, to actually use the phone?

Overall, I'd much prefer inflight wifi access. That would be sweet, and have much less impact on surrounding pax.

Cheers.