Jeb Corliss, who is from New Mexico, is a world famous wingsuit flyer. He broke both legs clipping a ledge on Table Mountain in South Africa. He uses regular helium balloons suspended at various heights to gauge his clearance at certain places on his flights. A flyer in front of him caused the balloons to drop and the strings got tangled in a bush. They were too low and he hit. Fortunately, there was enough of a drop off on the other side that he could deploy his chute.