Way back in the 1950s one Lt Col David Simons as part of the pre Mercury USAF space exploration stuff flew a balloon up to 102,000 ft. Now he may have stayed within the Continental US but it may be worth looking the flight up to see how he went on, what approval he needed and ATC wise who he talked to.
There was another American, one Francis Gary Powers, who tried flying across unfriendly territory without approval and who, despite being over 70,000 feet up, did not fare well when he attarcted attention to himself.
Brian Shul, in a later model of aeroplane seems to have had more success as did the USAs space to earth glider recently retired.
Small meteorological balloons however, seem to wander round the globe with impunity all the time.
Research into all the above may help you.
Last edited by Dave Gittins; 22nd October 2013 at 16:03.