The Convair F-102 Delta Dagger fighter aircraft was part of the backbone of the United States air defenses in the late 1950s. Entering service in 1956, its main purpose was to intercept invading Soviet bomber fleets. The aircraft's development was long and troubled, and by the early 1960s it was being replaced by F-101 Voodoos and F-4 Phantom IIs. Many of the F-102s were transferred to United States Air National Guard duty by the mid- to late-1960s, and the plane left service altogether in 1976.