The US Air Force has disciplined 70 service personnel after nuclear warheads capable of unleashing the equivalent of 10 Hiroshima bombs were mistakenly flown across the US.
A Pentagon investigation found that air and ground crews took a "lackadaisical" approach to vital safety checks put in place during the Cold War.
In the incident on 30 August, a B-52 bomber took off from the remote Minot Air Force Base in North Dakota with 12 cruise missiles that were being taken out of commission and scheduled for burial at the opposite end of the country at a Louisiana air base. The warheads on the decommissioned missiles should have been replaced with dummies of the same weight, but personnel failed to notice that six of the 12 were fully operational nuclear warheads.
The 1,100-mile flight was the first time in 40 years that nuclear bombs have been flown over US territory without top-level authorisation, and the terrifying mistake was not discovered for 36 hours. When it was, it was deemed so serious that the Secretary of Defense, Robert Gates, and President Bush were both informed.
The Pentagon said that three colonels and a lieutenant-colonel have been relieved of their duties, while 65 air force members have been stripped of their permission to handle nuclear weapons. The munitions squadron commander at Minot had been sacked already – within days of the incident. The air force is still considering possible criminal charges and further disciplinary measures.
Air force Major General Richard Newton said the Pentagon's six-week investigation uncovered a series of security lapses, shoddy visual checks and failures to consult records that would have revealed the error. He said: "The day-to-day mission out in the weapons storage area under the munitions control was lackadaisical."
Maj Gen Newton said a member of the bomber crew examined only one side of the payload – the side with the correct dummy warheads. The B-52 had sat on the tarmac at Minot overnight, with nothing but routine security patrols guarding its payload, and then for a further nine hours at the Barksdale base in Louisiana.
The Air Force Secretary, Michael Wynne, said: "This was an unacceptable mistake and a clear deviation from our exacting standards. We hold ourselves accountable to the American people and want to ensure proper corrective action has been taken."
Mr Wynne called the incident a one-off, the result of "an unprecedented string of procedural errors", and added: "We would not be this upset with ourselves, nor be striving to restore confidence, if this did not involve nuclear weapons."
The air force insists that the US public was never in danger and that even if the bomber had crashed, fail-safe mechanisms would have ensured that the bombs could not detonate.
Anti-nuclear campaigners said there was a danger that fissile material inside the warheads could have been released into the atmosphere if there had been an accident.
Hans Kristensen of the Federation of American Scientists said a government investigation more than a decade ago revealed concern over standards, and said the best service personnel have been lured to posts elsewhere. Mr Kristensen said: "Part of the reason is that after the end of the Cold War, the nuclear career was not very sexy."Reuse content