The Minuteman III intercontinental ballistic missile was removed from the silo which was operated by the 90th Missile Wing in remote area of north-eastern Colorado.
The air force gave no further details, saying the report was classified.
In a brief summary, it said the missile "became non-operational" during a diagnostic test on 16 May 2014, according to the Associated Press news agency.
The next morning a "mishap crew" chief "did not correctly adhere to technical guidance`` during troubleshooting efforts, "subsequently damaging the missile".
The team chief and two of his airmen - who were not named - were removed from duty after the incident, the summary adds.
All three later returned to work after being retrained.
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