Flight management systems are multipurpose avionic computer systems that display navigational information and manage flight plans. They receive data from various sensors to interpret the position, heading, and speed of an aircraft and provide information to guide the aircraft to the desired destination. Flight management systems usually have a keyboard or touchscreen interface for pilot interaction and a small screen for data display. A navigational database contains the components of which the flight plan is comprised, including airport and runway locations, as well as various flight procedures such as departure routes, holding patterns, standard terminal arrival routes, and instrument approach procedures. The flight management system determines the position of the aircraft by interpreting signals from sensors such as global positioning system receivers and inertial reference systems. Comparing the aircraft position with the flight plan, the flight management system guides the aircraft to its destination by calculating the course to follow, which the pilot can follow manually or set the autopilot to follow.