It is a freeware CAD-style program that allows you to modify the facility data, and some of the visible scenery, used in Microsoft Flight Simulator (FS). The facility data that AFCAD works with is used by ATC to control user and AI aircraft at airports and to assign parking. It also controls the airport information that you see on the �map view�, GPS screen, flight planner, and start position set-up window in Flight Simulator. The visible scenery that AFCAD can modify includes runways, taxiways, aprons, and all associated markings and lights.