U.S. missile crew fall asleep on duty

The U.S. Air Force has revealed three ballistic missile launch crew members in North Dakota fell asleep while holding classified launch code devices this month.

Fortunately, catastrophe was averted.

An investigation by military and security personnel was launched.

The probe found the missile launch codes were outdated and remained secure, but the July 12 incident follows a series of mistakes by the U.S. Air Force.

Last month the country's Defense Secretary Robert Gates announced a shake-up of the force's leadership following a series of nuclear-related mishaps.