An Air Force nuclear missile unit failed a safety and security inspection this week, the second wing of its kind to stumble on tests this year.
The latest involves the 341st Missile Wing at Malmstrom Air Force Base in Montana, which operates about a third of the 450 Minuteman III nuclear-tipped intercontinental ballistic missiles, according to an Air Force statement.
The wing received an "unsatisfactory rating" after making "tactical level errors" during one of several exercises conducted as part of the inspection.
A review is underway to determine accountability.
The errors were not related to the operation of nuclear missiles, one Air Force official said. The precise issue was not disclosed.
The wing, which includes about 3,000 personnel, was not "decertified" to conduct nuclear operations, which would have indicated a more significant failure.
Earlier this year, another wing, based at Minot North Dakota, did poorly in an inspection. That resulted in the removal of 17 military personnel from their jobs.
The third wing is located at F.E. Warren Air Force Base in Wyoming.