A coordinated group of instruments that provides the flight crew with information about the aircraft and its subsystems. Together with the controls, aircraft instruments form the human–machine interfaces that enable the flight crew to operate the aircraft in accordance with the flight plan. These instruments provide flight data, navigation, power plant performance, and aircraft auxiliary equipment operating information to the flight crew, air-traffic controllers, and maintenance personnel. While not considered as instrumentation, communication equipment is, however, directly concerned with the instrumentation and overall indirect control of the aircraft.