Aerobatic flying involves performing impressive manoeuvres while in an aircraft. While some helicopters can perform a limited number of aerial tricks, aerobatic flying is usually performed in planes or gliders. Most of the manoeuvres involve spins, rolls and fast-paced turns, usually in a choreographed display. Aerobatic flying is actually extremely challenging for the pilot, and requires a much larger number of skills than standard flying. More recently aerobatic flying has become a judged sport in which competitors show off their best tricks and sequences to try to out-do their opponents. .