Andrews Air Force Base was designated on 24 June 1948, and in June 1950, Andrews rapidly became involved in combat readiness training for B-25 Mitchell medium bomber crews. Combat readiness training and proficiency flying for military pilots assigned non-flying duties in the Washington area have remained two key elements in the local mission since the establishment of the base. HQ Air Research and Development Command (later, Air Force Systems Command) moved to Andrews from Baltimore, 24 June 1958. With the construction of new facilities beginning in 1959, Andrews had become by early 1962 the primary USAF flight installation serving the Washington, DC, area with the closing of the runway at Bolling AFB.