In 1966 , United States Secretary of Defense Robert McNamara proposed cutting " Chrome Dome " flights because the BMEWS system was fully operational , the bombers had been made redundant by missiles , and $ 123 million ( $ as of ) could be saved . SAC and the Joint Chiefs of Staff opposed the plan , so a compromise was reached whereby a smaller force of four bombers would be on alert each day . Despite the reduced program and the risks highlighted by the 1966 Palomares B-52 crash , SAC continued to dedicate one of the aircraft to monitoring Thule Air Base . This assignment was without the knowledge of civilian authorities in the United States , who SAC determined did not have the " need to know " about specific operational points
Palomares B-52 crash
1966 Palomares B-52 crash
1968 Thule Air Base B-52 crash