Pictured is a U.S. Air Force photo of a B-52H taking off from Minot AFB, N.D. on June 17.

As the B-52 fleet of 75 bombers enters its seventh decade of service, most of the aircraft's modernization efforts--worth more than $20 billion--are facing risks, according to a new Government Accountability Office (GAO) report, which advises the Air Force to delay a production decision for the Commercial Engine Replacement Program (CERP) until the program analyzes recent cost growth and schedule delays in order to understand the risks behind approving CERP production. That production decision is not scheduled until the first…