LGM-35A Sentinel (US ICBM)

What it is

The LGM-35A Sentinel is a land-based intercontinental ballistic missile under development by Northrop Grumman for the US Air Force. It is a three-stage solid-fuelled ICBM intended to replace all 400 deployed Minuteman III missiles at three bases: F.E. Warren Air Force Base in Wyoming, Malmstrom AFB in Montana, and Minot AFB in North Dakota. The Sentinel will carry the W87-1 nuclear warhead and is designed to serve through at least 2075, making it a 50-plus-year commitment. Beyond the missile itself, the program includes entirely new silo structures, launch control centers, and a ground-based communications network, a scope that has proven far more expensive than original estimates assumed.

History

The predecessor Minuteman III entered service in 1970. By the 2010s the US Air Force had run three service-life extension programs on it, but aging infrastructure made another round impractical. The Air Force Nuclear Weapons Center issued a request for proposals in July 2016 under the then-name Ground-Based Strategic Deterrent (GBSD). Boeing and Northrop Grumman competed through a three-year Technology Maturation and Risk Reduction phase. Boeing withdrew in July 2019, citing what it called inherently unfair advantages for Northrop, which had acquired rocket-motor supplier Orbital ATK. The Air Force awarded Northrop a sole-source Engineering and Manufacturing Development contract worth US$13.3 billion in September 2020. The program was renamed Sentinel in September 2022. Through 2022 the baseline cost estimate stood at roughly US$95.8 billion; by early 2024 it had grown past US$125 billion.

Current state

The US Air Force notified Congress on 18 January 2024 of a critical Nunn-McCurdy breach, triggered when unit costs exceed 25% over baseline. The Under Secretary of Defense rescinded Milestone B approval and mandated Pentagon certification that the program remained essential, which was issued in 2024. Total estimated cost has reached at least US$141 billion, an 81% increase over the original US$62.3 billion 2015 estimate. The primary driver is infrastructure: new silos, launch command centers, and cabling rather than reusing Minuteman's 50-year-old facilities. As of the 2026 GAO review, the first flight test is planned for March 2028, a slip of roughly four years, and initial operational capability is projected in the early 2030s. Software design and metrics are still not finalized, a flagged risk. The FY2026 US defense budget requested US$3.7 billion; Congress added US$2.5 billion in reconciliation. Because of the delays, the Minuteman III may remain in service through 2050, 14 years longer than planned.

Relationships

Northrop Grumman is the sole prime contractor; its 2018 acquisition of Orbital ATK (now Northrop Grumman Innovation Systems) gives it control of the rocket-motor supply chain, which was the stated reason Boeing withdrew. Bechtel is a major subcontractor for the construction of new silos and launch facilities. The US Air Force Global Strike Command operates the current Minuteman III force and will operate Sentinel; the Air Force Nuclear Weapons Center manages the acquisition. Oversight sits with the US Office of the Secretary of Defense for Acquisition and Sustainment, and the US Government Accountability Office and Congressional Research Service track the program annually. The 2026 restructure effort is the immediate operational context. The program intersects the broader arms-control environment: the New START treaty that capped deployed warheads expired in 2026, and Russia's expansion of its own land-based ICBM force, including the RS-28 Sarmat and mobile Yars systems whose launchers were targeted in the June 2026 Volgograd strike, adds political pressure to maintain the land leg.

What to watch

Whether the US Air Force closes the restructuring phase by end-2026 as planned, and whether the March 2028 first flight test holds. Software development timelines are the next near-term risk: the GAO flagged that design finalization and metrics are still outstanding as of early 2026. The Minuteman III sustainment burden will grow with every year of Sentinel delay; the US Air Force will need to plan operational test launches of Minuteman III post-2030 to sustain proficiency. Watch the FY2027 budget request for signs of further cost growth. Longer term, the sole-source structure limits the US government's leverage over Northrop Grumman on pricing, making independent GAO and CRS oversight unusually important for a program of this scale.