LGM-35 Sentinel

The LGM-35 Sentinel, also known as the Ground Based Strategic Deterrent (GBSD), is a land-based intercontinental ballistic missile (ICBM) system under development for the United States Air Force. It is intended to replace all 450 Minuteman III missiles beginning in 2029, with service expected through 2075. The Minuteman III missiles are currently deployed in North Dakota, Wyoming, Montana, and Nebraska.

In 2020, the Department of the Air Force awarded Northrop Grumman a sole-source contract to develop the Sentinel after Boeing withdrew from the bidding process. Subcontractors include Lockheed Martin, General Dynamics, Bechtel, Honeywell, Aerojet Rocketdyne, Parsons, Textron, and others.

On 19 January 2024, the Air Force announced that program costs had increased to over $125 billion, significantly exceeding the initial $77.7 billion estimate, and that deployment would be delayed by two years. The cost and schedule overrun was classified as "critical", triggering a Nunn–McCurdy review. Under Nunn–McCurdy, programs in critical status are presumed terminated unless the Department of Defense certifies that they are essential to national security and no less costly alternatives exist. It was determined that the Sentinel program met these criteria, allowing it to continue, however the Air Force was directed to implement cost controls. The review, released on 8 July 2024, also included a revised cost estimate, putting total acquisition costs at $140.9 billion.

The Air Force plans to procure 634 Sentinel missiles, along with 25 additional missiles for development and testing, to support the deployment of 400 operational missiles. The program also includes modernization of 450 silos and more than 600 facilities across approximately 40,000 square miles (100,000 km²). However, it was later determined that existing Minuteman silos could not be adapted for the Sentinel, requiring new silos to be constructed at significant additional expense not accounted for in the prior acquisition costs.