St Thomas, ON
You're telling me that the highly specialized antenna radiation pattern of cell towers is such that they *expect* to send and recieve signals from several miles *above* their ground-plane? Why would a cell tower waste their energy transmitting signals UP when their intended coverage area is within 100 feet (altitude) of the area surrounding them?
Basically, you will probably always be able to make a call from a plane if it's at 2000 ft or lower, but next to impossible to get a working signal higher than 8000 ft.
All this talk of laws pertaining to cell phone use on planes is B-crap, because aside from take-off, landing and taxiing, cell phones simply don't work above a few thousand feet.