I'm not brave enough to test altitude. The Tello is so light it would certainly fly away if flown to high. I usually keep mine no higher than 30-feet. On a windless day I've taken it up to about 50-feet, but just for a few moments. I would imagine you'd need to figure out a way to get the repeater in between your phone/yourself, and the tello which would be above you. Not sure how to get that one done.