Sentinel ICBM Gets New Silos, Reopening Its Environmental Review
The Air Force will study new Sentinel ICBM silo sites at three bases after finding that converting Minuteman III silos put key milestones out of reach.
On 9 October 2026, the Department of the Air Force published a notice of intent in the Federal Register to prepare a supplemental environmental impact statement (SEIS) for the LGM-35A Sentinel, the intercontinental ballistic missile (ICBM) designed to replace the Minuteman III. The filing formalizes a change the service announced earlier this year: Sentinel will not move into the old Minuteman III silos. It will get new ones.
The notice gives the reason in plain terms. The original approach to recapitalizing “all existing [Minuteman III] infrastructure could not be carried forward because key Sentinel Program milestones were no longer achievable due to cost and schedule risks associated with converting existing Launch Facility (LF) sites to Launch Silo (LS) sites.” The Air Force said it has restructured its basing approach “from legacy facility reutilization to the construction of modernized, new-built LS sites.”
What the notice proposes
The study updates the 2023 environmental impact statement and record of decision for replacing every land-based Minuteman III at F.E. Warren Air Force Base in Wyoming, Malmstrom AFB in Montana and Minot AFB in North Dakota.
| Item | What the Air Force says | Source |
|---|---|---|
| New silos | Up to 30 new launch silo sites at F.E. Warren and up to 60 at Malmstrom and Minot | Federal Register |
| Land | Purchases for new silo and launch center sites at F.E. Warren and Minot; field expansion to the northwest at F.E. Warren and to the west and east at Minot | Federal Register |
| Malmstrom | Former 564th Missile Squadron areas reused as swing space, plus temporary construction laydown areas | Federal Register |
| Old sites | Closure in place of a selected number of the current 150 Minuteman III launch facilities in each field; disposal of old launch and alert facilities | Federal Register |
| Footprint | Up to 12 acres per silo site and up to 16 per launch center; 150 operational silo sites kept at each field during the transition | Sentinel SEIS website |
| Infrastructure | New utility corridors, including fiber-optic cable not evaluated in 2023; MH-139 Grey Wolf helicopter refueling and rearming at selected launch centers | Federal Register |
| Timeline | 30-day public scoping period from publication; draft SEIS in fall 2027; final SEIS and record of decision in spring 2028 | Federal Register, SEIS website |
Table compiled by Peter’s World from the sources linked in each row.
The notice keeps the 2023 plan on paper as a “No Action Alternative” but calls it “not a reasonable alternative because it has been deemed unachievable due to cost, schedule, siting, and engineering constraints.”
How Sentinel got here
On 18 January 2024, the Air Force told Congress that Sentinel had triggered a critical breach under the Nunn-McCurdy statute. According to the Congressional Research Service, the Air Force initially estimated a unit-cost increase of at least 37 percent, from $118 million to $162 million in 2020 dollars.
On 8 July 2024, then-Pentagon acquisition chief William LaPlante certified the program to continue. The Office of Cost Assessment and Program Evaluation estimated total acquisition costs at $140.9 billion, 81 percent above the estimate at the September 2020 Milestone B decision. Most of the growth sat in the command and launch segment: launch facilities, launch centers and the conversion from Minuteman III. LaPlante rescinded Milestone B, ordered a restructure and said, “There are reasons for the cost growth, but there are no excuses.”
In February 2026, the Air Force laid out its reset plan: finish the restructure and reach a new Milestone B by the end of 2026, conduct a first missile pad launch in 2027 and deliver initial capability in the early 2030s. The service said building new silos “avoids the unpredictable costs and safety hazards of excavating and retrofitting 450 unique structures built over 50 years ago.”
Key program facts
- Predecessor: LGM-30 Minuteman III, in the force since 1970 (CRS).
- Prime contractor: Northrop Grumman (CRS).
- Quantity: 634 missiles planned, plus 25 for development and testing (CRS).
- Propulsion: three solid rocket motor stages; Stage 1 completed qualification testing in March 2025 and Stage 2 in July 2025 (Air Force).
- Warhead: initially the W87-0 now on Minuteman III; the NNSA plans a first production W87-1 in fiscal 2033, and Lockheed Martin is developing its Mk21A reentry vehicle (CRS).
- Budget: $4.6 billion requested for fiscal 2027 (CRS).
Testing and the schedule debate
On 14 September, the Air Force announced that an inert Sentinel had been stacked on a test pad at Vandenberg Space Force Base, California, Air & Space Forces Magazine reported. Air Force Secretary Troy Meink said the 2027 test launch timeframe still holds. Gen. Dale White, who oversees Sentinel as director of critical major weapon systems, told reporters, “We’re still on track for Milestone B.” On cost, he said, “I don’t think we’re anywhere near a number right now,” and the magazine reported that he treats the roughly $141 billion figure as a cap.
The Government Accountability Office has given a later date. Its February 2026 snapshot said first flight had slipped about four years and was planned for March 2028. GAO also wrote that software progress “remains slower than anticipated” and that delays may force the Air Force to operate Minuteman III through 2050, 14 years longer than planned.
Congress has set its own floor. Federal law requires at least 400 on-alert ICBMs, and the fiscal 2026 defense authorization act requires them to be spread across “not fewer than 450” silos at the three bases, CRS noted.
Why it matters
Peter’s World analysis, based on the sources cited in this article.
Sentinel is the land leg of a nuclear triad that is being rebuilt all at once, alongside the Columbia-class submarine and the B-21 Raider bomber. The 2024 review located most of Sentinel’s cost growth in ground infrastructure, and this notice starts the environmental review required to replace that infrastructure outright. In our view, that makes the SEIS a test of whether the restructure fixes the original problem rather than relocating it.
The schedule leaves little slack. The environmental record of decision lands only a few years before the early-2030s initial capability target, and new land purchases in Wyoming and North Dakota add landowners and agencies to the process. Those steps could become schedule drivers, though no official source has said so.
What to watch: the Milestone B decision and the restructured cost estimate, public comments filed during scoping, the first pad launch at Vandenberg and the draft SEIS.
Sources
- Department of the Air Force, Notice of Intent To Prepare a Supplemental Environmental Impact Statement for the Sentinel Deployment and Minuteman III Decommissioning and Disposal, Federal Register, 91 FR 64644, 9 October 2026.
- Department of Defense, Department of Defense announces results of Sentinel Nunn-McCurdy Review, via Air Force Nuclear Weapons Center, 8 July 2024.
- Secretary of the Air Force Public Affairs, Delivering deterrence: Sentinel restructure to complete in 2026; initial capability timeline set, 17 February 2026.
- U.S. Government Accountability Office, National Security Snapshot: ICBM Modernization Faces Critical Risks and Opportunities (GAO-26-108755), 18 February 2026.
- Congressional Research Service, Defense Primer: LGM-35A Sentinel Intercontinental Ballistic Missile (IF11681), updated 6 May 2026.
Additional sources
- Air & Space Forces Magazine: Air Force Stacks Inert Sentinel ICBM Ahead of First Test in 2027, 14 September 2026: Meink and White remarks and the $77.7 billion 2020 cost baseline the magazine reported.
- Sentinel SEIS project website: Proposed Action: per-base siting details: at Malmstrom, up to 30 new silo sites on acquired land plus up to 60 on former 564th Missile Squadron sites; at Minot, up to 60 on land west and east of the field.
- Air Force Nuclear Weapons Center: Sentinel ICBM (LGM-35A): the center calls Sentinel “the largest construction project in Air Force history” and says the first Minuteman III silo at F.E. Warren was taken offline in September 2025.
