"I have absolutely no reason to think at this point that this was an aircraft-wide or fleet-wide situation," Air Force Secretary Deborah Lee James said at an Air Force Association breakfast. "It appears as though it was a one-off situation."
The incident occurred Wednesday during a training flight near Minot Air Force Base, officials confirmed to Military.com. The engine broke up and debris landed in an unpopulated area. No injuries were reported.
The Cold War-era bomber stayed airborne to "burn up some fuel" before landing safely back at base, James said.
While the investigation into the incident ordered by Col. Matthew Brooks, commander of the 5th Bomb Wing, will take months, James divulged the base leadership's preliminary findings from her time there this week.
"It appears what happened was there was a catastrophic failure of one engine," she said. "Literally, I'm told, it conceivably disintegrated and, upon disintegration, came out of the aircraft."
James said aircrews believe that the engine is now "at the bottom of a riverbed" in an unpopulated area in North Dakota, "which will make it more complex in recovering the engine" for forensic analysis.
"Clearly, this is not something that happens all the time," she said. "But we train our people in an array of possibilities and worst-case scenarios, and this was a worst-case scenario."
The planes are among the oldest in the fleet. Three generations of airmen have flown the B-52 in combat, from Vietnam to Afghanistan, and the newest B-52 is more than a half-century old.
When asked whether this gives "more urgency" to a re-engining or modernization program for the B-52, James said, "It does not. I don't want anybody to think that the B-52 fleet isn't a fine, safe-flying, well-operating fleet."
"Mission capable rates are excellent," she said of the heavy bomber, known throughout the force as the BUFF, or "Big Ugly Fat Fellow."
There is interest in adding new engines to the B-52 down the line -- more to gain better fuel-efficiency than any other reason, James said.
"Could we save money or the life cycle costs?" she said. "Because, of course, modern-day engines are more fuel efficient, and there's a variety of ways where, if we were to re-engine, it would be a significant upfront cost, but maybe it would save us over the course of a life cycle."
The Air Force is reviewing the financial case for such a program, James said. As it stands now, the service has prioritized other upgrades to the B-52 in its five-year spending plan, she said.
"Timing is everything. Here I go to Minot, North Dakota, and boom an engine comes out of a B-52," the secretary joked. "So no cause and effect, but timing is everything."