Fcc rules for cell phone transimissions...?

im doing a project with a couple of my friends and we are sending a balloon into the air and are planning to communicate with it through at&t's background network. are there any fcc rules regarding the maximum height above sea level that cell phone signals can be transmitted because this is supposed to go to about a hundred thousand feet. or is in that a place where this kind of stuff is written. im just curious because i dont want to interfere next to the airplane signals.
Check FCC.GOV

OK We have sent amateur radio equipment up with balloons and the most problematic entity was dealing with the FAA for airspace.
The cell phone companies don't like individuals using cells on airplanes because of the phone trying to access multitudes of cell towers at the same time. With the all digital systems immediately it may not make any difference. It may be legal, just a aggravation to the phone companies.