On this topic, I have used mobiles (cellphones) in Australia up to 25,000 feet and had successful phone calls. This may have been with AMPS (analogue) but it may have also been with GSM (digital) technology.
Has anyone else ever been able to make successful calls at 25,000 ft or above?
Has anyone ever been able to make successful calls at 25,000 ft or above in the US?