MINOT AIR FORCE BASE, N.D. (AP) — The Minuteman 3 nuclear missiles hidden in full view across the High Plains are not only huge, at 60 feet tall. They are really old, too.

And that is one reason why trouble keeps finding the nuclear Air Force.

The Air Force asserts with pride that the missile system, now more than 40 years old, is safe and secure.

But it also admits to fraying at the edges. There are time-worn command posts, corroded launch silos and an emergency-response helicopter fleet so antiquated that a replacement was deemed “critical” years ago.

That partly explains why missile corps morale has sagged and discipline has sometimes faltered, as revealed in a series of Associated Press reports documenting problems that prompted worry at the highest levels of the Pentagon.