A deadly B52 bomber crash off Guam last year was caused by part of the plane's tail assembly being set in the wrong position, a US Air Force investigation report said.

"Decisive and urgent steps" are needed to restore the US Air Force's respect for nuclear weapons after three ballistic missile crew members fell asleep while holding classified launch code devices, US authorities said today.

Nuclear-armed missiles were flown across the US by mistake, military chiefs admitted for the first time.

The US Air Force dropped manslaughter and assault charges today against a fighter pilot who mistakenly bombed Canadian troops in Afghanistan, killing four soldiers.