“Inactive idle time describes when a [U.S. Navy] attack submarine designated for decommissioning cannot be inducted into a dry dock in a shipyard. As a result, the submarine and its crew must remain pier-side until a shipyard has the capacity in a dry dock to defuel their nuclear reactor.”
That’s a quote from a Government Accountability Office (GAO) report released last Thursday titled, Actions Needed to Address Costly Attack Submarine Maintenance Challenges, which describes lost operational days for the Navy’s 44 nuclear attack submarines (20 Los Angeles class and 24 Virginia class), including those spent awaiting depot maintenance or what’s called active idle time.
The Navy, according to the GAO report, said that as of fiscal year 2025, its 44 attack submarines “provide the United States an asymmetric advantage to gather intelligence undetected and attack enemy targets, among other missions. These capabilities make attack submarines some of the most requested assets by the global combatant commanders.”
However, the GAO found, “Over the last 10 years, the U.S. Navy has lost more than 15,000 operational days due to maintenance delays and idle time on active attack submarines. These delays resulted in an estimated $3.4 billion in costs to sustain crews and submarines that provided no operational capability.”
Along with the inactive idle time illustrated earlier, active idle time is a period when an attack submarine and its crew must remain pier-side because they cannot be taken in by a shipyard for maintenance and are no longer certified to conduct normal underwater operations.
Attack submarines follow the Fleet Response Training Plan which calls for a 12-month training and then a complex certification process that leads to deployment. Deployments are normally six months, although one could be longer, but the result is generally an 18-month cycle.
Thereafter, a nuclear attack sub goes through three or four operational cycles – around six years of operations – before the next major overhaul.
“From fiscal years 2016 through 2025, “ the GAO report said, “the U.S. Navy incurred 8,906 days of active idle time for active attack submarines, hitting its peak in fiscal year 2022 with 1,518 days. Since this peak, the U.S. Navy reduced active idle time to 166 days in fiscal year 2025.”
From fiscal years 2021 through 2025, according to the GAO report, the average depot-level maintenance period was 809 days. “Further, the U.S. Navy only completed about 11 percent of attack submarine depot maintenance on time at the public shipyards, from fiscal years 2016 through 2025,” the GAO report added.
For Los Angeles-class subs, active idle time is costing almost $220,000 per day for the entire group. For the Virginia-class, that figure is more than $237,000 per day.
Los Angeles class attack submarines have an expected life of 30 to 33 years, while the planned life for the newer Virginia class is 33 years.
According to the GAO, only U.S. public naval shipyards -- Portsmouth Naval Shipyard, Norfolk Naval Shipyard, Puget Sound Naval Shipyard, and Pearl Harbor Naval Shipyard -- provide depot maintenance for attack submarines, along with two private shipyards -- General Dynamics Electric Boat at Groton, Connecticut and Huntington Ingalls Industries Newport News Shipbuilding at Newport News, Virginia.
Inactive idle time for older Los Angeles class attack submarines is a growing problem.
This period, when an attack submarine designated for decommissioning cannot be taken into a dry dock in a qualified shipyard, requires that its crew must remain pier-side, according to the GAO report. That’s because “those required to maintain and supervise the nuclear reactor…must wait until a shipyard has the capacity in a dry dock to defuel their nuclear reactor,” the report said.
The decommissioning attack submarines “take limited dry dock space away from the operational fleet,” the GAO said, but added, “For most fiscal years prior [to 2025], 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.”
In fact, over the past five fiscal years, the Navy has had seven attack submarines waiting to decommission and has “incurred 2,216 days of idle time resulting in more than $480 million in operating and support costs,” according to the GAO.
“As of January 2026,” the GAO report added, “without mitigation, the U.S. Navy projects that 15 more attack submarines and their crews will enter inactive idle time from fiscal years 2026 through 2030.” That could see the Navy incurring “more than 14,000 days of inactive idle time and $3.1 billion in operating and support costs, according to our [GAO] analysis.”
Perhaps the worst example of inactive idle time, according to the GAO report, is the Los Angeles-class submarine USS Pasadena, which became inactive in January 2025, but is not expected to enter Norfolk Naval Shipyard for decommissioning until November 2028.
During this inactive idle time, which could run nearly four years, the Pasadena remains fully crewed and is being utilized by the Navy as a training platform. The inactive Pasadena has also been used in videos – in November 2024 for a promotional video for the 2024 Army-Navy Game, and in February 2025 for the Netflix TV series The Recruit.
A small group from the Pasadena crew remains on the submarine at all times to monitor security, nuclear reactor status, and safety systems. These crew members sleep in the submarine's cramped quarters during their off-watch hours, while on duty. The remainder of off-duty crew members may live on a tender ship, a submarine base barracks, or at their own off-base homes rather than on the submarine.
According to the GAO, the Navy “has not fully evaluated or established plans for implementing…alternative options for decommissioning attack submarines more efficiently and optimizing shipyard capacity for the operational fleet.”
For example, what about pier-side nuclear reactor defueling of inactive attack submarines which would not require now-limited dry dock space?
According to the GAO, “Navy officials stated pier-side defueling of the Los Angeles-class attack submarine nuclear reactors is not cost effective,” but those “officials were unable to provide documentation of detailed analyses conducted on the feasibility and cost-effectiveness of this option.” However, pier-side defueling is under study when it comes to the new Ohio-class strategic nuclear submarines, according to the GAO.
Another defueling option would be using floating dry docks, which the Navy officials told the GAO “requires additional study.”
Also under study by the Navy is to release a portion of the inactive attack submarine crew back to the operational fleet “over three phases: (1) the first month during system turnover to the public shipyard; (2) the first 6 months when idle conditions begin; and (3) nuclear reactor defueling once a dry dock is available.”
This approach has been used for two out of 18 Los Angeles-class subs set for decommissioning between 2014 and 2025, and, according to Navy officials, only “a limited number of attack submarines are planned to use this construct in the next five years.”
Asked why, “Navy officials cited public shipyard pier capacity constraints,” but again “did not provide documentation on any analyses conducted to reach this conclusion,” according to the GAO.
The Navy is studying whether the service life of two of its attack submarines by shifting, shortening or removing idle times. “As of September 2025, the U.S. Navy projected that it can reduce inactive idle time by 1,715 days for fiscal years 2026 through 2029 for [these] two attack submarines. However, these service life extensions are still pending approval,” the GAO said.
The GAO after this study concluded in its report, “While the U.S. Navy has recently made some progress in reducing attack submarine active idle time, inactive idle time has grown and will continue to grow with the impending wave of Los Angeles-class inactivations over the next 5 years.”
It then recommended the obvious: “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. Such options may include, but are not limited to, defueling outside of dry docks and reducing crewing for attack submarines awaiting decommissioning.”
I agree.
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