Myself, I lean to the explanation that this was in fact a simple but terrible screw-up. There are surely already plenty of American nuclear weapons on board subs and carriers in the Middle East, and even if some new ones were needed, there are plenty of ways to get them there without flying them loaded on B-52's across the country, and subsequently having the news leaked. I honestly believe they have the operational capability to carry out the real thing in secret. (I can't totally dismiss the idea that this was meant as a message, though usually sending such messages do not involve imposing radiation risk on civilian areas of the United States.)

The really important implication is beyond the immediate: The United States is in the beginning of a transition to a deep integration of nuclear and conventional capabilities. The Navy has already proposed, and the Air Force is about to propose, replacing some nuclear warheads on long-range ballistic missiles with conventional warheads. From outside the weapons will look the same.

The long-range bombers are already highly dual-capable and U.S. B-52s have been used repeatedly to launch conventional Air Launched Cruise Missiles against high-value targets. The Minot bomber was on its way to Barksdale, but it could hypothetically have been on its way to Iraq or - in a potential future conflict - North Korea, Iran or China with nuclear cruise missiles.

If the B-52 incident tells us that the military's command and control system cannot ensure with 100% certainty which weapons are nuclear and which ones are not, imagine the implications of the wrong weapon being used in a crisis or war. "Sorry Mr. President, we thought it was conventional."