ICBM Modernization: Air Force Actions Needed to Expeditiously Address Critical Risks to Sentinel Transition

What GAO Found

The Air Force has developed planning documents for the transition from Minuteman III to Sentinel but has not developed a risk management plan. The transition was planned to begin in fiscal year 2025, but those plans are on hold while the Department of Defense (DOD) restructures the Sentinel program. The Air Force developed an overarching transition strategy and a site transition plan for F.E. Warren Air Force Base in Wyoming, the first base scheduled to convert to Sentinel. However, the Air Force has not yet developed a transition risk management plan, a leading project planning practice. A detailed risk management plan would help the Air Force establish an organized, methodical way to identify, assess, and respond to the myriad risks, and better position the Air Force for a successful transition from Minuteman III to Sentinel.

While the Air Force has taken some actions to prepare operators, maintainers, and security forces for the transition, the Air Force has not developed a schedule for construction of a Sentinel test facility. The test facility is necessary early in the transition as part of a multistep process to revise policy and instructions that will be needed to prepare security forces for the transition and concurrent operation of Minuteman III and Sentinel.

Air Force Missile Maintainer in a Missile Training Silo in Montana, March 2025

DOD is assessing options to meet strategic deterrent requirements during the transition, but delays require prolonged operation of Minuteman III. Air Force officials are assessing options to potentially operate Minuteman III through 2050. However, prolonged operation presents sustainment risks. Addressing these risks in a transition risk management plan would help ensure the intercontinental ballistic missile (ICBM) system meets requirements during the transition.

This is a public version of a classified report that GAO issued in April 2025. This public version omits some information on plans and capabilities, the Sentinel test facility, and strategic deterrent requirements DOD deemed to be sensitive or classified.

Why GAO Did This Study

The U.S. has operated the land-based Minuteman III ICBM system for over 50 years, well past the original intended service life of 10 years. The system includes more than 600 facilities, including 450 missile silos, across five states. The replacement system, Sentinel, faces critical cost overruns and schedule delays. The Air Force must continue to operate and maintain the aging Minuteman III system to meet U.S. strategic deterrent requirements until Sentinel is fully fielded.

A report accompanying a bill for the National Defense Authorization Act for Fiscal Year 2024 includes a provision for GAO to review the Air Force's planning for the transition from Minuteman III to Sentinel ICBM. This report addresses the extent to which the Air Force (1) planned for the transition and concurrent operation of Minuteman III to Sentinel, (2) developed plans to prepare operators, maintainers, and security forces for the transition, and (3) developed plans to meet strategic deterrent requirements during the transition. GAO collected and reviewed relevant documents and interviewed DOD and Air Force officials about transition planning efforts.