BISMARCK, N.D. – The missile wing commander at North Dakota’s Minot Air Force Base was relieved of his command Wednesday after a series of missteps at the unit, including two crashes of vehicles carrying missile parts.

Col. Christopher Ayres was not ousted for any misconduct or wrongdoing, but the Air Force said it had lost confidence in his ability to command the base’s 91st Missile Wing given recent incidents.

The 91st Missile Wing oversees 150 Minuteman III missiles, sunk in hardened silos, in central and western North Dakota.

“It comes down to performance and accountability,” said Air Force spokeswoman Laurie A. Arellano. “With nuclear weapons, our nation expects no less than perfection.”

Ayres had been the base missile wing commander since May 2008.

During his tenure, three ballistic missile crew members fell asleep holding launch codes in July 2008 and were discharged a year later.

Also in July 2008, a vehicle carrying a rocket booster for an unarmed Minuteman III ballistic missile overturned while being transported from the base to a launch facility in northwestern North Dakota. And this August, a semitrailer carrying rocket engine parts from the base overturned when the driver became distracted by an insect that flew in a window and landed on the driver’s back, the military said.