The 646th Aircraft Control Squadron was the operational USAF unit of Highlands Air Force Station and manned a flight at Texas Tower 4, a Highlands offshore radar annex from 1959 until it collapsed into the Atlantic Ocean in 1961, killing 28 people. The squadron was activated on 1 June 1948 and renamed the 646th Aircraft Control and Warning Squadron on 6 December 1949, then 646th Radar Squadron (SAGE) on 1 Oct 1958.