One of the more publicized U.S. false alarms took place in November 1979. A technician at NORAD -- the North American Air Defense Command -- accidentally placed a training tape into the main systems at NORAD's Cheyenne Mountain Complex in Colorado. That mistake made NORAD's early warning system computer think the United States was undergoing a massive Soviet missile attack -- and it responded by alerting NORAD officials.
Within minutes, they realized the error. The incident was one of five missile warning system failures that took place over an eight-month period between 1979 and 1980. It also prompted a government reassessment of NORAD and its operations.