Assigned to the 393d Bomb Squadron, 509th Composite Group, it was built at the Glenn L. Martin Aircraft Plant at Omaha, Nebraska, accepted by the Army Air Forces on April 3, 1945, and flown to Wendover Army Air Field, Utah, by its assigned crew B-10 (Capt.
It was originally assigned the Victor (unit-assigned identification number) number 8 but on August 1 was given the triangle N tail markings of the 444th Bomb Group as a security measure and had its Victor changed to 88 to avoid misidentification with actual 444th BG aircraft.
The name is a word play on the colloquial idiom "Up and at 'em", meaning "There is a lot of work to be done," and referencing the unit's atomic mission.
Up An' Atom returned to the United States with the 509th CG in November 1945 to Roswell Army Airfield.
It was transferred to the U.S. Navy and used as a target at the Naval Ordnance Test Station at China Lake, California.