Modern paratroopers are highly trained soldiers capable of fighting behind enemy lines for long periods of time. They use a variety of techniques including HALO (high altitude, low opening) jumps, which permit covert insertion of paratroopers -- the transport plane flies too high to be detected, and the paratroopers open their chutes too low for the chutes to be spotted by the enemy. Virtually all military Special Forces training includes parachute training, since it is a key element of modern commando operations.