1960: On 5 October, radar at a missile early-warning station in Greenland showed enemy missiles heading towards the United States.
At North American Air Defense Command headquarters in Colorado, a “massive” Soviet ballistic missile attack appeared imminent, until someone realised that Nikita Khrushchev was actually visiting New York. It seemed very unlikely that the Soviet Union would launch missiles that might kill its own leader. Huge relief at NORAD headquarters, no doubt.
What the radar had in fact detected was a reflection from the moon, rising slowly over Norway.
Source: Eric Schlosser, Command and Control (2013), pp. 253–4