Last month I asked Robert McNamara, the secretary of defense during the Kennedy and Johnson administrations, what he believed back in the 1960s was the status of technical locks on the Minuteman intercontinental missiles. ... McNamara replied ... that he personally saw to it that these [PAL's] ... were installed on the Minuteman force, and that he regarded them as essential to strict central control and preventing unauthorized launch. ... What I then told McNamara about his vitally important locks elicited this response: “I am shocked, absolutely shocked and outraged. Who the hell authorized that?” What he had just learned from me was that the locks had been installed, but everyone knew the combination. The Strategic Air Command (SAC) in Omaha quietly decided to set the “locks” to all zeros in order to circumvent this safeguard. During the early to mid-1970s, during my stint as a Minuteman launch officer, they still had not been changed. Our launch checklist in fact instructed us, the firing crew, to double-check the locking panel in our underground launch bunker to ensure that no digits other than zero had been inadvertently dialed into the panel. SAC remained far less concerned about unauthorized launches than about the potential of these safeguards to interfere with the implementation of wartime launch orders. And so the “secret unlock code” during the height of the nuclear crises of the Cold War remained constant at 00000000.
Training exercises can be mistaken for the real thing. In 1979, a test tape, simulating a Russian attack was mistakenly fed into a NORAD computer connected to the operational missile alert system, resulting in an alert and the launching of American aircraft [Borning 1988].