A graphic illustration of LGM-35A Sentinel. (Jim Masie/Northrop Grumman)
Software delays related to the U.S. Air Force’s future LGM-35A Sentinel intercontinental ballistic missile could pose “significant risks” to the program, requiring the U.S. to continue using the existing LGM-30G Minuteman III arsenal for longer than expected, the Government Accountability Office said Wednesday.
The first flight of the new Sentinel is unlikely to occur before March 2028, according to the GAO report.
The timeline runs counter to a U.S. Air Force news release issued Tuesday that said the Sentinel could receive a new Milestone B rating, allowing for a prototype, by the end of the year. The Air Force said that it believed the missile’s first flight could occur in 2027.
The Air Force said Thursday that it was aware of the GAO report but felt confident that the accelerated timeline it presented this week was accurate.
“The Air Force has made tremendous progress since the GAO reports were written, and the Sentinel program is on track to complete its restructure by the end of 2026,” the service said in a statement.
The new missile would be the land-based piece of the United States’ nuclear triad, along with submarine-launched ballistic missiles and manned bombers.
The Sentinel program’s cost is now pegged at about $141 billion, including construction of 600 silos and other facilities.
The new ICBM program exceeded statutory cost thresholds in January 2024, delaying the development of a prototype. The so-called Nunn-McCurdy unit cost limits created by Congress govern the pace of spending on defense programs. Specifics were not immediately available on Thursday.
The GAO said the delay could allow the service time to address issues in the program.
The GAO report said the Sentinel program is four years behind schedule, requiring a 14‑year life extension of the Minuteman.
The Los Alamos Study Group Exchange Monitor, a publication for nuclear weapons experts, reported in January 2025 that the last Minuteman III would likely not be decommissioned until 2050 or later, as the two programs overlap during the Sentinel rollout.
An unarmed LGM-30G Minuteman III sits inside the silo of U-01 at F.E. Warren Air Force Base, Wyo., July 9, 2025. (Michael A. Richmond/U.S. Air Force)
