The New Mile-High Club
The US Federal Aviation Administration (FAA) last year established an objective to continue assessment of PED (Personal Electronic Devices) threat. The FAA will study how and whether the operation and transmission of mobile devices affects a plane's systems. They do not expect to draw any conclusions until 2006.
Should the FAA approve the use of wireless devices on planes in the US, the Federal Communication Commission (FCC) has already begun taking steps to make it possible for those devices to communicate with base stations on the ground. It has reserved 4 MHz of spectrum in the 800 MHz band for transmission of wireless communication from air to ground. Currently the FCC has limited use of this spectrum to wireless data, however it has begun asking for public opinion on opening the spectrum up to cellular phone calls as well.
In either case, your phone or laptop / PDA would not be communicating directly with networks on the ground, but with a tiny base station on the plane called a "picocell" that would then communicate to networks on the ground for you. These picocells are the basis for all next generation air-to-ground systems.