I'm skeptical that it really causes trouble for phone networks. In my experience flying small airplanes, getting a signal is easy below about 4,000ft, starts getting spotty up to 6,000ft, and is basically impossible above that. Which makes sense: antennas at the cell will be aimed sideways, not up, so the only cells you might be able to talk to would be really far away.
And this is in a fiberglass airplane that's basically radio transparent. Now try it in an aluminum airplane at 30,000+ft. I doubt the cells can even hear your phone in the first place.
-You're quite possibly right - I cannot recall having heard cell phones go off while at cruise, but during approaches it happens if not all the time, then at least every once in a while when I fly somewhere. (Me being a good boy, I've never tried to satisfy my curiosity by keeping the phone on during flights. :))
There's enough radio transparent openings in an aircraft fuselage for it to be a reasonably inefficient faraday cage - say, windows, for instance. (Or are those portholes on an aircraft, too?)
As far as I know they are still called windows. And yes, you'll be able to connect when close to the ground in many cases. The metal body will greatly attenuate signals, but won't block them completely, especially if you're near a window. The lower and slower you are, the more an airborne cell phone will look and act like a normal ground-bound one, so the less of a problem it'll cause for the network.
And this is in a fiberglass airplane that's basically radio transparent. Now try it in an aluminum airplane at 30,000+ft. I doubt the cells can even hear your phone in the first place.