Lockheed RC-121 Warning Star airplane model. The Warning Star entered service in 1955, with the final variants being retired from the US Air Force Reserve in 1978. The Warning Star pioneered the concept of Airborne Early Warning and Control, with units being used for fleet coverage, airborne extension of the Distant Early Warning (DEW) Line, support of the Apollo Space Program and other force coordination tasks. Throughout its life the Lockheed Warning Star was used to test experimental radar and electronic equipment installations.
A USAF RC/EC-121 made history in October 1967, when, while operating over the Tonkin Gulf off North Vietnam, it guided a US Fighter to the successful interception of a VNAF Mig-21, the first time an airborne controller had directed a successful attack, setting the stage for many future developments in the arena of AEW&,C.