How high/far can a hanglider go?
This depends a lot on the conditions in which it is flown, but flights in excess of 300 miles in length and altitudes of well over 20,000 ft. MSL have been recorded. (These last have all been with FAA permission for the rules lawyers reading this). More typically, pilots in the summer in the western US will frequently achieve altitudes of 5,000 to 10,000 ft AGL and fly for over 100 miles.
