# U.S. LGM-35A Sentinel ICBM development > Live situation record from CLSTR: https://clstr.news/situations/us-lgm-35a-sentinel-icbm-development > Updated: 2026-09-20T17:28:17.000Z. Sources: 7. Developments: 2. The United States is modernizing its land-based nuclear deterrent through the development of the LGM-35A Sentinel intercontinental ballistic missile (ICBM). Developed by Northrop Grumman for the U.S. Air Force, the three-stage, solid-fuel missile is intended to replace the aging Minuteman III system. The program involves a comprehensive infrastructure overhaul, including the construction of new launch silos, communication networks, and command-and-control systems across bases in Wyoming, Montana, and North Dakota. The goal is to maintain an inventory of over 450 missiles and hardened silos. Recent technical milestones include the successful vertical assembly of an inert Sentinel missile at Vandenberg Space Force Base as part of the ‘Pathfinder’ exercise. This assembly validated the integration of missile stages and propulsion elements, while a Critical Design Review confirmed that the hardware meets safety and performance requirements. The program is currently targeting flight testing in 2027, though it continues to manage challenges related to cost overruns and software risks. ## Timeline ### 2026-09-20: LGM-35A Sentinel ICBM to modernize U.S. nuclear deterrent Northrop Grumman is developing the LGM-35A Sentinel ICBM to modernize the U.S. nuclear triad, replacing the 50-year-old Minuteman III with new missiles and expanded command-and-control infrastructure. 3 sources. https://clstr.news/cluster/lgm-35a-sentinel-icbm-to-modernize-us-nuclear-deterrent ### 2026-09-14: Northrop Grumman and U.S. Air Force assemble Sentinel missile for 2027 flight tests Northrop Grumman and the U.S. Air Force completed the vertical assembly of an inert Sentinel ICBM, a major step toward scheduled flight testing in 2027 to replace the Minuteman III system. 4 sources. https://clstr.news/cluster/northrop-grumman-and-us-air-force-assemble-sentinel-missile-for-2027-flight-tests --- Cite as: U.S. LGM-35A Sentinel ICBM development. CLSTR, https://clstr.news/situations/us-lgm-35a-sentinel-icbm-development