Oct. 19 (Bloomberg) -- Three senior officers have been relieved of command for their roles in mistakenly allowing a B-52 bomber to fly from North Dakota to Louisiana carrying armed nuclear warheads, top Air Force officials said.

A six-week-long inquiry uncovered a series of procedural errors that led to the unauthorized transfer of the six warheads, said Major General Richard Newton, assistant deputy chief of staff for Air Force operations.

``Our investigation found that there has been an erosion of adherence to weapons handling standards'' at the bases at both ends of the flight, Newton said during a Pentagon news briefing. ``This was an unacceptable error that resulted in an unprecedented string of procedural failures.''

The bomber took off from Minot Air Force Base in North Dakota on Aug. 30 with the nuclear-armed cruise missiles under one wing. The mistake wasn't discovered until after the plane landed later that day at Barksdale Air Force Base in Louisiana.

The missiles were to be ferried from Minot to Barksdale for eventual decommissioning.

The three senior officers relieved of duty this week were Minot's wing commander and maintenance group commander and Barksdale's operation group commander, all of them colonels, Newton said. He declined to name them, citing privacy concerns.

Series of Mistakes

Newton narrated a long string of mistakes by Air Force personnel at Minot, starting on Aug. 29 with the misidentification of a ``pylon'' of six missiles sitting in a storage warehouse as ready to be shipped to Barksdale.

The missiles were supposed to have had their live nuclear warheads removed and replaced with inactive ones. That was not done, Newton said.

After that first mistake, Air Force personnel had four opportunities that day and the next to discover the error during required checks, he said. Each time, they failed to do so because they didn't follow proper procedures.

The missiles with the live warheads -- as well as a second group of six missiles with inactive ones -- were loaded onto the B-52 and stayed there on the flight line overnight, Newton said.

Protected

He said the warheads were protected in that location because the entire base is a secure facility. He acknowledged that the level of security is higher inside the storage facility.

The bomber took off from Minot on the morning of Aug. 30 and arrived at Barksdale nearly three hours later, according to a time line provided by the Air Force. The fact that the six missiles carried live warheads was discovered by crew members at Barksdale about nine hours after the B-52 landed, when the missiles were taken off the plane.

``This was an unacceptable mistake and a clear deviation'' from service standards, Air Force Secretary Michael Wynne said at the briefing. The service is ``making all appropriate changes to make sure this has a minimal chance of ever happening again and we would like to make sure it can never happen again.''

Defense Secretary Robert Gates said yesterday it was his goal to ``reduce to the lowest level humanly possible'' the chance of a repeat incident.

In addition to the Air Force investigation, Gates has asked former Air Force Chief of Staff Larry Welch to do an independent review of the incident and report to him. That report is still pending.

To contact the reporter on this story: Ken Fireman in Washington at kfireman1@bloomberg.net

Last Updated: October 19, 2007 17:54 EDT