vortex,
I always wondered and you may know the answer: a few years back I flew in a hot air balloon once and I was greatly surprised I couldn't use my GSM (old Sony cdm-1000) a few hundred feet over a friend's house in a small town with good GSM-coverage. According to the pilot this is (was?) normal from a balloon, yet exactly one year ago several calls were made from a jet whose fate we all know.
Can you enlighten me?