Airborne early warning and control
During the mid-1950s, planners devised the idea of extending the wall of powerful land-based radar seaward with Airborne early warning and control units. This was done by equipping two wings of Lockheed RC-121 Warning Star aircraft, the 551st Airborne Early Warning and Control Wing, based at Otis Air Force Base, Massachusetts, and the 552nd AEWCW, based at McClellan Air Force Base, California, one wing stationed on each coast. The RC-121s, EC-121s and Texas Towers, it was believed, would contribute to extending contiguous east-coast radar coverage some 300 to 500 miles seaward. In terms of the air threat of the 1950s, this meant a gain of at least 30 extra minutes warning time of an oncoming bomber attack. ADC's Operation Tail Wind on 11–12 July tested its augmentation plan that required Air Training Command interceptors participate in an air defense emergency. A total of seven ATC bases actively participated in the exercise, deploying aircraft and aircrews and supporting the ADC radar net. As the USAF prepared to deploy the Tactical Air Command E-3 Sentry in the later 1970s, active-duty units were phased out EC-121 operations by the end of 1975. All remaining EC-121s were transferred to the Air Force Reserve, which formed the 79th AEWCS at Homestead Air Force Base, Florida in early 1976. The active duty force continued to provide personnel to operate the EC-121s on a 24-hour basis, assigning Detachment 1, 20th Air Defense Squadron to Homestead AFB as associate active duty crews to fly the Reserve-owned aircraft. Besides monitoring Cuban waters, these last Warning Stars also operated from NAS Keflavik, Iceland. Final EC-121 operations ended in September 1978.