Skydiving is a sport involving a skydiver jumping down from an airplane while it is flying and parachuting to the ground. Skydiving can be done individually and with other people. Training is required to go solo. The jump can also be made from a helicopter or the bottom of a hot air balloon from 4000m or 13,000 ft. Some thrill seekers attempt to skydive without a parachute whilst flying through the air, and instead rely on the small parachutes they have professionals put on them.