A relay in an aircraft is an electrically controlled switch that allows a low-power control circuit to switch high-power electrical systems. Relays are an essential component of efficiently and safely distributing electrical power to aircraft systems, such as avionics, lighting, fuel pumps, and landing gear systems.

Aircraft relays are two broad categories: electromechanical and solid-state. Electromechanical relays utilize physical contacts to open and close circuits, whereas solid-state relays use semiconductor technology for quicker operation and extended life. Both are built to resist harsh aviation environments such as vibrations, temperature changes, and electromagnetic interference.

By reducing electrical arcing and optimizing system automation, relays enhance operational efficiency and flight safety. They also minimize pilot workload by automating significant electrical processes. Used in commercial and military aviation, aircraft relays play an integral role in providing reliable power distribution and smooth aircraft operation.