WASHINGTON (AP) — Failings last spring by nuclear missile operators at an Air Force base in North Dakota were worse than first reported, according to documents obtained by The Associated Press.

Airmen responsible for missile operations at Minot Air Force Base would have failed their portion of a major inspection in March 2013 but managed a “marginal” rating because their poor marks were blended with the better performance of support staff – like cooks and facilities managers – and they got a boost from the base’s highly rated training program. The “marginal” rating, the equivalent of a “D” in school, was reported previously. Now, details of the low performance by the launch officers, or missileers, entrusted with the keys to missiles have been revealed.