- The maintenance team chief "mistakenly performed an action not directed by the technical guidance"
- Air Force officials say the 2014 incident did not result in injuries or any threat to public safety
- Three airmen who lost certification have been retrained and are back on the job
The incident occurred when the Minuteman III nuclear missile, assigned to the 90th Missile Wing at F.E. Warren Air Force Base in Wyoming, became "non-operational" during a diagnostic test, according to a statement released by the Air Force.
While troubleshooting the issue, the maintenance team chief "mistakenly performed an action not directed by the technical guidance," the statement said.
Air Force officials did not specifically address whether radioactive material was released when the missile was damaged, but said the incident did not result in any injuries or threaten public safety.
Further details about the nature of the "mishap" are murky, as the full report from the military's Accident Investigation Board remains classified.
The Air Force insists that the maintenance team chief was properly trained for the task he was performing but made a mistake that resulted in damage to the missile. Following the incident, the airmen were retrained and have returned to duty.
In response to the incident, the Air Force said it has "strengthened technical guidance, modified training curriculum, and shared information with the other missile wings regarding the conditions that led to the mishap."
The Minuteman III is the only land-based intercontinental ballistic missile system used by the United States and is one component of its nuclear triad. The other two parts of the triad are the Trident submarine-launched ballistic missile and nuclear weapons carried by long-range strategic bombers.
First deployed in the 1960s as part of the U.S. nuclear deterrent program, the Minuteman system is supposed to ensure that missiles can be launched quickly and at any time.
Missiles are dispersed in hardened silos and connected to an underground launch control where crews are on standby around the clock.
The United States currently has 450 Minutemen III missiles at Warren AFB, Malmstrom AFB in Montana and Minot AFB in North Dakota.