US Air Force officers have accidentally left often blast doors at critical nuclear missile sites twice in 2013 alone the AP has reported.
The news agency claims that two officers with access to missile launch keys have left often doors designed to prevent terrorists entering the sites.
The blast doors are supposed to be shut at all times if one of the crew members is asleep - as was apparently the case in these instances.
The danger is that an intruder might be able to get hold of secret launch codes or other critical information.
Known as "missileers", the crew in charge are supposed to be on constant alert - even though they are unlikely to ever be called into action. The result, the AP says, is low morale and a series of lapses.
The AP said that officials "with direct knowledge" of Air Force intercontinental ballistic missile sites, said that there have been many more violations that these two cases, but that most have gone unreported.
A series of other problems in the keeping of the nuclear arsenal, including failed safety inspections and the firing of the two-star general in charge last week have been revealed in recent weeks.
Luckily the 'blast doors' (secured by 12 hydraulically operated steel pins) are not the first line of defence. A terrorist trying to gain access would first have to access a 100m elevator shaft, thwart many security cameras and defeat regular patrols of armed guards.