VATSIM is short for Virtual Air Traffic Simulation Network and it connects individuals flying online or acting as virtual Air Traffic Controllers. The system is a flight simulation that connects devotees who act as a pilot or air traffic controller. Clearly players swap the two roles but requirements are very different for each position. Players learn how active air traffic controllers are and how little time they have for each pilot. When approaching an airport the air traffic controller explains the initial clearance, where he wants you, what altitude to be at, the speed, and the heading. So he gives many facts in a single sentence. Pilots need to accept and understand that information. The air traffic controller has no time to repeat because there may be fifteen airplanes in the pattern. VATSIM allows bad things to occur but it does forbid certain simulations like a person declaring a hijacking or duplicating terrorist flights.