During 1956, deliveries to the USAF commenced. A total of 145 RB-66Bs would be produced. In service, the RB-66 would function as the primary night photo-reconnaissance aircraft of the USAF during this period; accordingly, many examples served with tactical reconnaissance squadrons based overseas, typically being stationed in the United Kingdom and West Germany. A total of 72 of the "B-66B" bomber version were built, 69 fewer aircraft than had been originally planned. A total of 13 B-66B aircraft later were modified into EB-66B electronic countermeasures (ECM) aircraft, which played a forward role in the Cold War between the United States and the Soviet Union, and were stationed at RAF Chelveston with the 42nd Tactical Reconnaissance Squadron, who performed the conversion during the early 1960s. They would rotate out of an alert pad in during the time that the 42nd had them.