Defense Primer: LGM-35A Sentinel Intercontinental Ballistic Missile

Updated May 6, 2026

Defense Primer: LGM-35A Sentinel Intercontinental

Ballistic Missile

The LGM-35A Sentinel is envisioned as an intercontinental

ballistic missile (ICBM) system that is expected to replace

the Minuteman III (MMIII) ICBM in the U.S. nuclear force

structure. MMIII has served as the ground-based leg of the

U.S. nuclear triad—land-based ICBMs, submarinelaunched ballistic missiles, and nuclear-capable bombers—

since 1970. The Department of Defense (DOD), which is

“using a secondary Department of War designation,” under

Executive Order 14347 dated September 5, 2025, requested

$4.6 billion for the Sentinel in FY2027, mostly for research,

development, test, and evaluation. The FY2027 budget

request for the Department of Energy’s National Nuclear

Security Administration (NNSA) included $913 million for

the W87-1 nuclear warhead for the Sentinel.

serve through 2075. The Air Force argued that, when

compared with a life-extended MMIII, a new ICBM would

meet current and expected threats, maintain the industrial

base, produce a modular weapon system, and reduce life

cycle cost. The Air Force and Northrop Grumman, the

Sentinel’s lead defense contractor, planned for the Sentinel

to begin replacing MMIII in 2029.

What Is an ICBM?

Figure 1. Sentinel Deployment and Support Locations

Program Status

The Air Force plans to procure 634 Sentinel missiles, plus

an additional 25 missiles to support development and

testing, to enable the deployment of 400 missiles. The Air

Force also originally planned to modernize 450 silos and

more than 600 facilities (see Figure 1).

A U.S. ICBM can reach targets around the globe in

approximately 30 minutes after launch. In the first three

minutes, three solid fuel rocket motors power the missile’s

flight. After the powered portion of flight, the missile

follows a parabolic trajectory toward its target. The missile

releases its warhead during the midcourse portion of its

flight, and the warhead continues to the target. Once the

President authorizes the launch of any U.S. ICBM, the

missile cannot be recalled or destroyed in flight. The same

is true for nuclear missiles launched from U.S. submarines.

In contrast, U.S. bombers can return to their bases without

releasing their weapons; their weapons also cannot be

recalled after their release.

The United States began deploying nuclear-armed ICBMs

in 1959 and has maintained these systems “on alert,” or

able to launch promptly, since that time. The Air Force

deployed the Atlas between 1959 and 1965, the Minuteman

beginning in the 1960s, and the Peacekeeper (or MX)

between 1987 and 2005. The Air Force bases its ICBMs in

hardened concrete silos, or launch facilities, located in

North Dakota, Montana, Wyoming, Colorado, and

Nebraska. The United States has periodically considered

alternative ICBM basing concepts to ensure survivability.

The Transition from Minuteman III

The MMIII, which currently is deployed in a singlewarhead configuration that could carry up to three

warheads, entered the force in 1970. The Air Force has

replaced and updated many of the component systems on

the missile—a process known as “life-extension”—several

times over the past 50 years. The Air Force has stated that

some of these components may face reliability concerns as

they reach the end of their intended lifespans. After

conducting an analysis of alternatives in 2014, the Air

Force decided to replace MMIII with a new missile system

(originally Ground Based Strategic Deterrent) that would

Source: Air Force Global Strike Command, 2023.

In January 2024, the Air Force informed Congress that the

Sentinel program exceeded its initial cost projections,

estimating at least a 37% increase (from $118 million initial

baseline cost to $162 million in 2020 dollars) in cost per

unit. This cost increase is known as a “critical” breach per

the Nunn-McCurdy Act (10 U.S.C. §§4371-4377), which

requires DOD to, absent termination, certify that the

program is essential to national security, has no cheaper

alternatives, and can be managed. Such a certification also

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Defense Primer: LGM-35A Sentinel Intercontinental Ballistic Missile

mandates that DOD develop new cost estimates and

program milestones and submit this information to

Congress. Air Force officials have attributed cost increases

to ground infrastructure updates.

In July 2024, DOD announced completion of the NunnMcCurdy review and that the program “met the statutory

criteria to continue.” DOD officials said the review resulted

in the rescindment of the Sentinel’s Milestone B approval

and cited a cost estimate of a “reasonably modified”

Sentinel at $141 billion. Air Force officials have said that

they are reexamining requirements and restructuring the

program to make the ground segment “simpler” and “more

affordable.” In December 2025, the Senate confirmed Air

Force General Dale White, who was assigned as Direct

Reporting Portfolio Manager to oversee several major Air

Force acquisition programs, including the Sentinel.

In February 2026, the Air Force announced that it

anticipates to “complete the [program] restructure and

achieve a Milestone B decision by the end of 2026” and

deliver an “initial capability targeted for the early 2030s.”

In April 2026 testimony, General White restated this

timeline and stated that “cost estimation will be completed

in the summer.” The Air Force now plans to build new

silos, instead of reusing old ones, a process that will

reportedly require a supplementary environmental impact

statement. The Army Corps of Engineers, rather than

Northrop Grumman, reportedly will now manage some of

the ground infrastructure updates. The Air Force said that it

plans to conduct a pad launch in 2027 at Vandenberg Air

Force Base in California. Northrop Grumman announced in

April 2026 that it is producing solid rocket motors for the

initial flight tests and constructing a prototype silo.

Warheads

The Air Force plans to initially deploy the Sentinel with the

W87-0 warhead currently on the MMIII. NNSA is

developing the W87-1 warhead and plans to deliver a first

production unit in FY2033. NNSA announced the

qualification of the first war reserve plutonium pit for the

W87-1 in October 2024. Lockheed Martin is developing the

Mk21A reentry vehicle for the W87-1. DOD and NNSA are

also modernizing the arming and fuzing assembly.

Considerations for Congress

ICBM Force Necessity

Some analysts have argued for the United States to reduce

or eliminate its ICBMs because they increase the risk of

accidental war or because the invulnerability of ballistic

missile submarines makes ICBMs “redundant.” Advocates

of retaining ICBMs have argued that these missiles are the

most “responsive” leg of the U.S. nuclear triad. The 2022

Nuclear Posture Review (NPR), a Biden Administration

review of U.S. nuclear policy, echoed past NPRs in stating

that the three triad legs are “complementary,” with each one

“offering unique attributes.”

MMIII Life Extension

Some Members of Congress have questioned the need to

fund and deploy new ICBMs; others have also suggested

that the Air Force reconsider MMIII life extension. They,

along with other commentators, have argued that a delay or

cancellation of the Sentinel could ease financial and other

pressures caused by the simultaneous recapitalization of all

legs of the nuclear triad. In 2021, DOD commissioned an

independent study on future ICBM options, which

recommended an assessment of MMIII life extension.

However, the 2022 NPR endorsed the Sentinel and said that

any alternative “would increase risk and cost.” Air Force

officials stated in January 2024 that they did not see a

“viable” long-term MMIII life extension, though they were

“committed” to doing “everything [they] can to keep it in

the field.” A September 2025 Government Accountability

Office (GAO) study stated that the Air Force may operate

the MMIII through 2050, though it faced parts obsolescence

and other sustainment risks. In April 2026 testimony,

General White stated that the Air Force “annually allocates”

more than $2 billion for MMIII sustainment and operations

and is carrying out a strategy to “provide a critical bridge”

through Sentinel deployment.

Sentinel Costs and Schedule

Some Members of Congress have been concerned about the

costs and schedule delays associated with the Sentinel, the

W87-1 warhead, and NNSA plutonium pit production.

Section 1629 of the National Defense Authorization Act for

Fiscal Year 2025 (NDAA; P.L. 118-159) imposed

conditional requirements on the program to ensure

oversight and opportunities for competition.

Risk of Sentinel Delays

Some Members of Congress have expressed concern about

the risks associated with transition from the MMIII to the

Sentinel. Since the FY2017 NDAA (P.L. 114-328, §1667),

Congress has required that the Air Force deploy no fewer

than 400 on-alert ICBMs. The FY2026 NDAA (P.L. 11960, §1632) amended law (10 U.S.C. §9062) to reaffirm this

minimum requirement and required that these ICBMs be

deployed equally across “not fewer than 450” silos at F.E.

Warren, Malmstrom, and Minot Air Force bases.

An Air Force official reportedly stated in January 2025 that

MMIII and Sentinel operations would overlap for at least

15 years. The GAO report assessed MMIII-to-Sentinel

transition risks and recommended that the Air Force

develop a transition risk management plan. Section 1641 of

the FY2026 NDAA mandated an Air Force strategy to

sustain the MMIII and maximize its end-of-life margin.

In Section 1650 of the FY2024 NDAA (P.L. 118-31),

Congress directed the Air Force to “develop a plan to

decrease the amount of time required to upload additional

warheads to the [ICBM] force.” Section 1633 of the

FY2025 NDAA limited the availability of certain DOD

funds pending the submission of this plan to Congress. The

2023 report of the Congressional Commission on the

Strategic Posture of the United States proposed considering

such upload to field “the same number of warheads” “if the

number of available [ICBMs] is reduced.” The commission

report also proposed that the Air Force consider deploying

the Sentinel with multiple warheads or with “some portion

of the future ICBM force” in a road-mobile configuration to

account for evolving nuclear threats to the United States

from Russia and China.

Anya L. Fink, Analyst in U.S. Defense Policy

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Defense Primer: LGM-35A Sentinel Intercontinental Ballistic Missile

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