Idle Navy Subs Could Cost $3.1 Billion In Maintenance Delays

Why It Matters

The U.S. Navy's attack submarine fleet faces a mounting crisis that threatens operational readiness while draining billions in taxpayer dollars on idle vessels. A recent GAO report published on August 27 reveals that submarines designated for decommissioning are sitting unused in shipyards, unable to be properly retired due to lack of capacity and planning. These vessels are consuming resources that could otherwise support the active fleet, which is already stretched thin by maintenance backlogs.

Attack submarines gather intelligence undetected and attack enemy targets, making them critical to national defense. They are among the most requested assets by global combatant commanders. Yet over the last 10 fiscal years from 2016 through 2025, the Navy lost more than 15,000 operational days due to maintenance delays and idle time on active submarines. That lost operational capacity came with an estimated $3.4 billion price tag for sustaining crews and submarines that provided no operational capability.

From fiscal year 2026 through 2030, the Navy could incur more than 14,000 additional days of inactive idle time on submarines awaiting decommissioning, potentially costing $3.1 billion to operate and support those vessels. Fifteen attack submarines will enter inactive idle time from fiscal year 2026 through fiscal year 2030 without mitigation.

The Bottleneck

The Navy's 44 active attack submarines depend on access to shipyard capacity for maintenance and repairs. When submarines designated for decommissioning cannot be inducted into dry docks because those facilities are full or unavailable, they enter a holding pattern called inactive idle time. This is distinct from active idle time, which occurs when operational submarines are waiting for maintenance. Both drain resources. Both reduce the number of submarines available for deployment.

Inactive idle time describes when an attack submarine designated for decommissioning cannot be inducted into a dry dock in a shipyard. The Navy has made recent progress in reducing active idle time, but inactive idle time for attack submarines has grown and is projected to worsen without mitigation.

The GAO examined 10 years of Navy maintenance data and found a systemic failure to plan for decommissioning. The Navy has not fully evaluated alternative options to more efficiently decommission attack submarines, nor has it developed and implemented an inactivation plan that could reduce inactive idle time for crews and submarines. These are not technical gaps but planning failures, the GAO concluded.

What the GAO Found

The public version of GAO report GAO-26-109256 is a declassified version of a classified report GAO issued on July 16, and GAO analyzed U.S. Navy attack submarine maintenance data from fiscal years 2016 through 2025. The Department of Defense omitted classified or sensitive information from the public version, including attack submarine operational availability and how the U.S. Navy's approach to force generation compares to strategic competitors' approaches.

The GAO made two specific recommendations to address the crisis. First, the Secretary of the Navy should ensure that the Chief of Naval Operations directs the Naval Sea Systems Command to fully evaluate alternative options for decommissioning attack submarines more efficiently to optimize shipyard capacity for the operational fleet. The GAO suggested that alternative decommissioning options may include defueling outside of dry docks and reducing crewing for attack submarines awaiting decommissioning.

Second, the Secretary of the Navy should ensure that the Chief of Naval Operations directs the Naval Sea Systems Command to develop and implement a plan for attack submarine inactivations that reduces inactive idle time for crews and submarines. The inactivation plan should include steps to achieve objectives and timeframes for monitoring and mitigating risk for inactive idle time reduction.

Both recommendations are currently "Open," meaning actions to satisfy the intent of the recommendations have not been taken or are being planned. The U.S. Navy verbally concurred with the GAO's recommendations but did not provide written comments.

The Investigation

The investigation originated from congressional direction. House Report 118-529, produced by the House Committee on Armed Services and accompanying the Servicemember Quality of Life Improvement and National Defense Authorization Act for Fiscal Year 2025, included a provision directing the GAO to assess the readiness and availability of the Navy's attack submarine fleet. Congress recognized that submarine maintenance had become a concern and tasked the GAO with an independent audit.

The GAO reviewed Navy documentation and interviewed officials to develop its findings. The analysis covered fiscal years 2016 through 2025, capturing a full decade of maintenance trends and identifying patterns of deterioration.

The Fiscal Reckoning

The financial burden is staggering. Over the past 10 years, maintenance delays on attack submarines resulted in substantial costs to sustain crews and submarines that provided no operational capability. That money went toward keeping vessels operational while they sat idle, unable to contribute to national defense.

Without mitigation, the Navy could incur $3.1 billion in costs to operate and support inactive submarines from fiscal year 2026 through fiscal year 2030 alone. That is nearly equivalent to what was already spent over the prior decade, but compressed into just five years. The trajectory suggests the problem will compound unless the Navy implements the GAO's recommendations immediately.

The cost reflects a structural problem: the Navy is spending to maintain decommissioned submarines as if they were operational assets. Crews remain assigned, utilities remain powered, and maintenance continues even though these vessels will never return to service. The inefficiency is baked into current procedures.

The Bottom Line

The GAO's recommendations target the root causes. Alternative decommissioning methods could free up dry dock capacity currently consumed by submarines awaiting retirement. Defueling submarines outside of dry docks, for instance, would reduce the time each vessel occupies scarce shipyard space. Reducing crewing for attack submarines awaiting decommissioning is among alternative decommissioning options that GAO's first recommendation identifies.

As of now, the Navy has not committed to written responses outlining how or when it will act. Congress may need to follow up to ensure the recommendations translate into action before the projected costs materialize.

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