Seventy years after entering service, the B-52 Stratofortress is undergoing a massive modernization that will transform it into the B-52J—but the ambitious upgrade program is already running years behind schedule and billions over budget.

The Air Force marked the bomber’s 70th anniversary in June 2025, celebrating an aircraft that first took to the skies in 1955 and shows no signs of retirement. The final B-52H model entered service in May 1961 and remains active today, making it one of the longest-serving military aircraft in history.

“For seven decades, the B-52 has stood as a symbol of American airpower,” U.S. Strategic Command said in its commemoration. “The longevity of the B-52 is a testament to both the airframe’s robust original design and the Air Force’s continued investment in modernization.”

But that continued investment is hitting serious obstacles.

The Engine Upgrade Is Three Years Behind

The centerpiece of the modernization effort—replacing the bomber’s aging engines with modern Rolls-Royce F130 turbofans—won’t reach initial operational capability until 2033, three years later than originally planned, according to a Government Accountability Office report.

The Air Force selected the Rolls-Royce F130 engine in 2021 under a contract worth up to $2.6 billion to provide 608 engines and spares for the fleet of 76 B-52H bombers. The F130 will replace the Pratt & Whitney TF33 engines—a 1950s-era design that has been out of production since 1985 and is extremely costly to operate and maintain.

The re-engining program has hit delays as an inlet redesign pushes the critical design review into 2026. According to the GAO, delays stem from ongoing engine inlet issues discovered during design testing and from Boeing’s lag in submitting proposals needed for maturing the program’s cost and schedule baselines.

The full re-engining effort is now planned to be completed by 2036, potentially slipping from the original 2035 target. That would extend the total time between the original Commercial Engine Replacement Program (CERP) contract award and completion to around 15 years.

Radar Upgrade Also Struggling

The B-52 Radar Modernization Program is facing its own set of problems. The program is now not expected to field an upgraded radar until as late as 2030—a delay of roughly three years—as officials struggle to modernize the Eisenhower-era bomber.

The program plans to replace the current APQ-166 radar on all 76 B-52H aircraft with a modern Active Electronically Scanned Array (AESA) radar. But the program experienced a Nunn-McCurdy cost breach in May 2025, requiring the Air Force to notify Congress of significant cost increases.

According to the GAO’s annual weapon systems assessment, the radar program “continues to struggle with schedule delays while mitigating cost increases.” The program office delayed the first and second low-rate production decisions by 11 months each.

What the Upgrades Will Deliver

Once complete, the modernization will dramatically improve the B-52’s capabilities and sustainability.

The new Rolls-Royce F130 engines will deliver substantially better fuel economy and reduce maintenance demands. The upgrades are expected to cut sustainment costs and provide operational benefits including extended range. The new engines will also increase electrical power generation capacity and provide modern digital engine controls and displays.

The AESA radar upgrade will sharpen targeting and situational awareness, giving the bomber modern sensor capabilities comparable to contemporary aircraft.

Vice Adm. Richard Correll, who was confirmed to lead Strategic Command in November 2025, testified at his confirmation hearing that the upgrades are “essential” and that the B-52 will ultimately resemble “basically a new airplane.”

The Broader Implications

The delays and cost overruns have implications beyond the B-52 itself. Air Force Chief of Staff Gen. David W. Allvin testified to the Senate Armed Services Committee that if the B-52 upgrade “goes worse than we hope, then we would need more funding for the B-21.”

The Air Force currently plans to acquire at least 100 B-21 Raider stealth bombers, the service’s newest aircraft. If B-52 modernization costs continue to spiral or delays worsen, pressure will mount to accelerate B-21 production to maintain bomber fleet capability.

Keeping an Icon Flying

Despite the setbacks, the Air Force remains committed to keeping the B-52 flying into the 2050s—nearly a century after the design first took shape.

Maj. Gen. Jason Armagost of Eighth Air Force said the upgraded “J model” will include “new engines, radar systems and weapons upgrades” and serve “as the physical embodiment of the idea of peace through strength and carry us into the 2050s.”

Boeing is leading the integration effort, with work taking place at facilities where engineers can climb inside and around an actual B-52 loaned from the boneyard to more quickly identify problems and solutions.

The question now is whether the Air Force can deliver on its modernization promises—and whether the iconic bomber that has served for seven decades can successfully navigate the challenges of entering its eighth.