An automatic means for steering an aircraft or other vehicle. The original use of an autopilot, or automatic pilot, was to provide pilot relief during cruise modes. Autopilots now perform functions more rapidly and with greater precision than the human pilot. The functions, designs, and uses of autopilots vary widely depending on the type of vehicle. In addition to controlling various types of aircraft and spacecraft, autopilots are used to control ships or sea-based vehicles and in some cases land-based vehicles. This article discusses autopilots used in aircraft and space vehicles.