Avionics are electronic components and subsystems intended to be integrated into the core functions of an aircraft. Some of the constraints that apply to avionics, as opposed to electronics in general, are the need not to interfere with other systems, to meet the space, weight and environmental constraints of aircraft, and to be maintainable.
All modern aircraft have avionics for flight control, navigation, communications, and safety. While flight controls operated by the crew, or an autopilot, once were linked mechanically or hydraulically to engines and aerodynamic steering structures, most controls are "fly by wire", with the actuation of the engine or aerodynamic component by local electric motor(s). These systems are often interconnected with multiple levels of redundancy in case of electrical failure.
Military aircraft have a wide range of avionics for detecting threats and targets, fire control and defensive systems, the latter primarily being forms of electronic warfare. While early aircraft ran wires to individual components, the trend went to common bus standards such as MIL-STD-1553, and increasingly to ruggedized versions of COTS communications media such as Gigabit Ethernet.