MINOT (AP) - The military has named a new commander at Minot Air Force Base in the wake of a cross-country flight of a B-52 bomber armed with six nuclear-tipped cruise missiles.

The former commander, Col. Bruce Emig, who also served as the 5th Bomb Wing commander, was relieved of command in the wake of the bomber flight from the base to Barksdale Air Force Base in Louisiana.

Vice commander Col. Paul G. "Greg" Bell has been promoted to replace Emig, said Maj. Patricia Traynor, the base spokeswoman.

The Air Force conducted a six-week investigation into the bomber flight Aug. 29-30. The military called the episode an "unacceptable mistake."

Air Force Secretary Michael W. Wynne said changes are being made to ensure there is a minimal chance of such an incident ever happening again.

The Air Force also said it has punished 70 airmen involved in the accidental cross-country flight. Emig is being reassigned, but the military has not said where.

"Their reassignment is a demonstration of the accountability inherent in leadership," Bell said.

Maj. Gen. Richard Newton, the Air Force deputy chief of staff for operations, said Friday that adherence to weapons-handling standards had become lax at Minot and Barksdale.

Bell called the bomber flight incident "a rare mistake and a breakdown in procedures" and said he has confidence in the airmen at Minot Air Force Base.

"We take with the utmost seriousness our responsibilities to protect and safeguard weapons, and we understand that there is zero tolerance for errors," he said.

Bell, a graduate of the U.S. Air Force Academy in Colorado Springs, Colo., has been in the Air Force for more than 20 years. He is a pilot with more than 3,000 flying hours and more than 200 combat hours, flying a total of 33 missions in operations Desert Storm and Enduring Freedom. He became vice commander of the 5th Bomb Wing in July 2006.

Bell has served in a broad range of assignments, including as an instructor at the U.S. Air Force Weapons School and the U.S. Naval War College.