[2] From December 1946, it performed routine training duties in the Air Force Reserve through 27 June 1949 when it was inactivated due to budget reductions.

Under ADC the 21st AD was placed under First Air Force and assumed the jurisdiction of the former New York Air Defense Sector, controlling interceptor and radar units over eastern Pennsylvania, New Jersey, the New York City/Long Island area and the coast of Connecticut, Rhode Island and Massachusetts, including Cape Cod.

During this time, it participated in air defense training exercises, accomplished live and simulated intercepts, and directed numerous flying sorties until inactivation in December 1967[2] as part of an ADC consolidation of intermediate level command and control organizations, driven by budget reductions required to fund USAF operations in Southeast Asia.

The 21st AD was reactivated in November 1969 under Aerospace Defense Command (ADCOM) at Hancock Field, New York.

(Approved 17 July 1952) This article incorporates public domain material from the Air Force Historical Research Agency