Klein wrote:

Given that it's no big deal these days to make a multi-mode,
multi-band phone, why do you think it'd be so tough to make a
multi-mode, multi-band base station in the A/C? Certainly would be
easier if all phones were CDMA, of course. ;-)

That would be fine if there were some industry cooperation with the
people planning on offering the airborne service. But the plethora
of incompatible modulation schemes now sort of demonstrates that this
level of cooperation isn't likely .