Submarine maintenance delays have cost the Navy $3.4 billion over the past decade and could add $3.1 billion more as it prepares to retire aging Los Angeles-class attack submarines, a new Government Accountability Office (GAO) report finds.
In an analysis of attack submarine (SSN) data from fiscal years 2008 to 2025, GAO said it found “persistent depot maintenance delays, increased lengths of depot maintenance periods, and increased idle time.”
The report said the Navy incurred 3,040 maintenance day delays from 2016 to 2020 and another 3,454 delay days from 2021 to 2025 while the average deport-level maintenance period from 2016 to 2020 was 744 days versus 809 days for fiscal years 2021 to 2025. The Navy also only finished about 11 percent of SSN depot maintenance on time at the four public shipyards from fiscal 2016 to 2025.
Beyond delay days, GAO found the Navy incurred 8,906 active idle time days for active SSNs from fiscal 2016 to 2025. That peaked at 1,518 active idle time days in 2022 and that has lowered to 166 days in fiscal 2025. Active idle time is when the submarine and its crew have to remain pierside because it is not certified for normal operations and has to wait for its maintenance period.
Overall, GAO calculated this means the Navy lost over 15,000 operational days to the delay and idle time delays.
Another factor that pressure on the Navy is impending increases in inactive idle time, meaning submarines and their crews waiting years to be inducted into a public shipyard for decommissioning due to shipyard constraints. While idling, the boats and their crews cannot conduct normal operations and must remain pierside while certifications expire, but they are still fully crewed with sailors, including those who must maintain and supervise nuclear reactors.
Ultimately, those boats will have to wait until a shipyard has space for the submarine to dock and defuel the reactor. The four public naval shipyards’ priorities are conducting maintenance on the nuclear-powered aircraft carrier and nuclear ballistic missile submarines over active SSNs, let alone those due for inactivation services.
Then, once an inactive SSN is inducted into a dry dock, it still retains the crew and takes limited dry dock space away from operational vessels.
“Inactive attack submarines faced significant increases of idle time over the last ten years, incurring 3,287 days from fiscal years 2016 through 2025, reaching a peak of 1,260 days of inactive idle time in fiscal year 2025,” GAO said. “For most fiscal years prior, one or two attack submarines entered inactive idle time each year. However, without mitigation, the U.S. Navy projects a significant increase of inactive idle time through fiscal year 2030.”
The report recommended that the Chief of Naval Operations direct the Naval Sea Systems Command to fully evaluate alternative options for decommissioning attack submarines more efficiently to optimize shipyard capacity for the operational fleet and that the Naval Sea Systems Command be ordered to use that evaluation to develop and implement a plan for attack submarine inactivation to reduce inactive idle time.
GAO cited a recent example of the growing problem, the case of the Los Angeles-class USS Pasadena (SSN-752). As the Pasadena entered inactive idle status on Jan. 1, it is not expected to be able to get into the Norfolk Naval Shipyard to begin its inactivation process until Nov. 15, 2028, a wait of 1,414 days.
Navy officials told the GAO auditors the service is trying to maximize the utility of that inactive submarine by using it as a training platform.
“However, this extended delay is costing the U.S. Navy over $300 million in operating and support costs over its nearly 4 year inactive idle period, according to our analysis,” GAO said.
GAO estimated that over fiscal 2026 to 2025, the Navy spent about $4.2 billion in 2025 dollars on SSNs sitting idle for all reasons while waiting to enter shipyards combined with those delayed in completing shipyard maintenance. The estimate was based on costs of crewing, maintaining and supporting SSNs.
The report said while the Navy agreed with and implemented four recommendations from a previous 2018 report on SSN maintenance periods starting late, including using private shipyard capacity for maintenance periods, inactive periods are still steadily worsening.
“Although the U.S. Navy has not eliminated the attack submarine maintenance backlog, it has made significant progress in reducing attack submarine active idle time …While the U.S. Navy has reduced active idle time, we found inactive attack submarine idle time has grown and will continue to worsen. The U.S. Navy incurred 2,216 days of idle time on seven attack submarines waiting to decommission over the past five fiscal years—resulting in more than $480 million in operating and support costs. We found this challenge will likely worsen as more Los Angeles-class attack submarines are planned for decommissioning over the next five years,” the report said.
As of January, the GAO said without further mitigation efforts, the Navy projects that 15 attack submarines will enter inactive idle time from fiscal 2026 to 2030, making the Navy incur over 14,000 more days of inactive idle time and a further $3.1 billion in costs to operate and support otherwise inactive submarines.
The increases are tied to plans for the retirement of Los Angeles-class submarines while simultaneously dealing with new Virginia-class submarines replacing them.
GAO said Navy officials said the service has examined some ways to help alleviate inactive idle time, including pierside defueling, reduced crewing for inactive submarines and service-life extensions for SSNs to gain more operational time.
“However, we found the U.S. Navy has not fully evaluated or established plans for implementing these alternative options for decommissioning attack submarines more efficiently and optimizing shipyard capacity for the operational fleet,” the report said.
GAO warned that without fully evaluating alternative options for decommissioning SSNs more efficiently amid growing inactivation requirements and implementing a plan with timeframes that can reduce inactive idle time, the Navy will not be able to fully employ its crews, optimize public shipyard capacity or reduce costs of idling submarines and thus not reduce the projected billions in costs and thousands of idle days.
GAO said it previously provided a draft of a classified version of this report to the Navy in April with two additional recommendations the service deemed sensitive. The Navy “verbally concurred with the recommendations in this report, but did not provide written comments.”
Exchange Monitor affiliate Defense Daily first published a version of this story.
