LGM-35A Sentinel

The hardest infrastructure project in Air Force history — the LGM-35A Sentinel is the intercontinental ballistic missile meant to replace the 1970-vintage Minuteman III as the land leg of the US nuclear triad: 400 deployed missiles, 450 launch sites, service into the 2070s. It is also America's most troubled strategic program: a critical cost breach in 2024 drove the estimate from $78 billion to at least $141 billion, the plan to reuse Minuteman silos was abandoned for digging entirely new ones, first flight has slipped four years to 2028, and the missile it replaces may now have to soldier on toward 2050.

Overview

The Sentinel — the Ground Based Strategic Deterrent (GBSD) until its 2022 naming — is the US Air Force's program to recapitalize the entire land-based leg of the nuclear triad: the 400 deployed Minuteman III ICBMs sitting in 450 silos across Wyoming, Nebraska, Colorado, Montana and North Dakota, plus the launch-control centers and cabling that make up more than 600 facilities in all. Northrop Grumman won the $13.3 billion engineering and manufacturing development contract in September 2020 as the sole bidder, with the original plan of record calling for 659 missiles, initial operational capability around 2029, and service to 2075. The missile itself — three solid-fuel stages, digitally engineered, modular by design, carrying the W87 warhead family — has largely hit its marks: full-scale qualification firings of Stage 1 (March 2025) and Stage 2 (July 2025) went cleanly. The program around it has not. A critical Nunn-McCurdy breach declared in January 2024 concluded in a certified 81 percent unit-cost growth — at least $141 billion — a rescinded Milestone B, and a root-and-branch restructuring whose central discovery was that the cost lives in the ground, not the missile: converting 55-year-old Minuteman silos proved riskier than digging entirely new ones, a decision formalized in May 2025. As of mid-2026 the restructure is due to complete by year-end, IOC is officially "the early 2030s," and the Government Accountability Office warns Minuteman III may have to serve 14 years longer than planned — through 2050.

Development

The Sentinel began as the GBSD program, awarded to Northrop Grumman on 8 September 2020 for $13.3 billion after Boeing withdrew over Northrop's acquisition of the solid-rocket-motor maker Orbital ATK, per SpaceNews — a sole-source start critics never stopped citing. The 2020 baseline priced acquisition at ~$77.7 billion with IOC in mid-2029. The reckoning came on 18 January 2024, when the Air Force notified Congress of a critical Nunn-McCurdy breach; the Pentagon's July 2024 review concluded 81 percent unit-cost growth — roughly $140.9 billion — yet certified the program as essential ("no alternatives" to 400 deployed missiles through 2070), rescinded its Milestone B baseline and ordered a restructuring, per Breaking Defense and the Arms Control Association. The structural culprit was command-and-launch infrastructure: in May 2025 the Air Force abandoned Minuteman silo conversion entirely — Sentinel will use predominantly new silos dug on existing missile-field land, per Defense News. Milestones since: Stage-1 and Stage-2 qualification static fires (March and July 2025), the first complete three-stage ground-test missile, the first Minuteman III silo taken offline (September 2025), and groundbreaking on a prototype silo at Promontory, Utah (February 2026), per US Strategic Command. The February 2026 GAO snapshot put the schedule plainly: first pad launch planned 2027, first flight from a representative silo March 2028 — four years late — with software running slow and no integrated risk-management plan yet for what the service calls its most complex infrastructure project ever.

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