Since the 1940s, with the improvement of aircraft electrical system, aircraft power distribution equipment began to be serialized. Standards and specifications were formulated in the mid-1950s. With the development of large aircraft, the weight of power distribution system occupies a major position in the total weight of aircraft power supply system. Some planes have thousands of circuit breakers, and the cable weight accounts for 70% of the total weight of the power supply system. At the end of 1960s, aircraft power distribution developed to solid-state power distribution controlled by multiplex transmission bus. Since 1970s, the electrical system has been cross-linked with electronics, weapons and control systems through multiple buses and controlled by computers.