In May 1963, the Air Force determined that all Atlas D missiles would be phased out of its inventory between 1965 and 1968. A year later, Secretary of Defense Robert McNamara directed this program be accelerated and the first Atlas D missile left Warren on 26 May 1964.SAC Missile Chronology, pp. 40-44 with the retirement of the Atlas D, the squadron became non operational in October 1964,Ravenstein, p. 211 and was inactivated on 1 December 1964.See Ravenstein, p. 211 (end of assignment to 389th Wing).See Mueller, p. 184 (end of assignment at F.E. Warren).
