Title: The Navy's Attack Submarines Have Costly Maintenance Challenges

Description: The Navy's attack submarine fleet provide the United States
with an unparalleled advantage to gather intelligence undetected and
attack enemy targets. But during the last decade, the Navy has lost
thousands of days of submarine use to costly maintenance delays.  We
learn more from GAO's Diana Maurer. 

Related work: GAO-26-109256, Navy Readiness: Actions Needed to Address
Costly Attack Submarine Maintenance Challenges

Released: August 2026


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{ Music }


[ Diana Maurer: ]

It's extremely important that the Navy gets maintenance right on a
submarine. But they're taking longer to repair the subs they have. 


[ Holly Hobbs: ]

Welcome to the Watchdog Report, your source for fact-based, nonpartisan
news and information from the U.S. Government Accountability Office--I'm
your host Holly Hobbs.

The Navy's attack submarines provide the United States with an
unparalleled military advantage. These subs are among the most requested
assets by military commanders around the globe. But during the last
decade, the Navy has lost thousands of days of submarine use to costly
maintenance delays. 

Here to tell us more about this issue is GAO's Diana Maurer. Thanks for
joining us! 


[ Diana Maurer: ]

Thank you.


[ Holly Hobbs: ]

Diana, maybe you could start with telling us a little bit about the
Navy's attack submarine fleet. How many are there and what do they do?


[ Diana Maurer: ]

Sure. So, the U.S. Navy has 44 attack submarines. These are subs that
the Navy uses to perform some very sensitive and important missions.
Most importantly, they're very quiet. They're nearly silent. They're
nuclear powered, which means they can go hundreds of feet underneath the
ocean. And because they're nuclear powered, they can travel pretty much
anywhere there is an ocean, they can go without having to refuel for a
very long period of time. 

These subs have extensive capabilities to collect intelligence and
information while they are silently gliding beneath the oceans. They
also have weapons. So, in time of conflict, they have torpedoes that the
sub can use to target enemy subs and enemy ships. They also have an
array of non-nuclear missiles that they can use to attack targets on
land as well as on sea. They provide the Navy a very critical capability
to perform a variety of missions. That means the Navy uses them a lot.
Another key thing to recognize about these attack submarines, and U.S.
Navy submarines in general, is that the Navy is very committed to
performing the necessary maintenance and safety checks on those subs. 

And for folks who want to learn more about the history of that you can
look into the history that--the tragic history--of the U.S.S. Thresher,
which was a submarine that the U.S. lost over 60 years ago. But coming
out of that catastrophe, the Navy is focused on maintenance and in their
mind, maintenance equals safety for the crew that operates these subs
that are often hundreds of feet beneath the ocean.


[ Holly Hobbs: ]

I guess I thought all subs were attack subs. Is there different kinds of
subs? Are there non-attack subs?


[ Diana Maurer: ]

So, the Navy has another class of submarines--ballistic missile
submarines. They call them the 'boomers.' That's the type of submarine
that carries nuclear missiles. They're part of the U.S. strategic triad.
That's a different group of subs. Our report did not look at the
boomers. We looked at the 44 attack submarines. So, the Virginia Class
and the Los Angeles Class attack submarines.  


[ Holly Hobbs: ]

So these are important assets. What's been the challenge in maintaining
them?


[ Diana Maurer: ]

There are a couple categories of challenges that the U.S. Navy faces in
maintaining attack submarines, and the first category is just inherent
to any submarine. It's extremely important that the Navy gets
maintenance right on a submarine because as we mentioned, the Navy
equates maintenance with safety. 

So, there's strict and stringent maintenance requirements. And if a
submarine does not meet them, it does not receive what the Navy calls
its dive certification, which means it's not allowed to go underneath
the water, which means it has no operational capability. So very high
standards that must be met all the time. So that's sort of one piece of
it. 

The other piece of it is that a submarine is not like a car. Like you're
doing maintenance on a car, you pop the hood. You do maintenance on an
airplane, you can take off a side panel and kind of rummage around and
fix things. Subs don't have those things. So, doing maintenance on a sub
is sort of like doing maintenance on your car's engine through the glove
compartment. It requires a lot of planning, a lot of technical
expertise. So, when the Navy is bringing its subs into port to do the
most substantial maintenance, called depot maintenance, they plan out
specifically what they're going to fix and what they're going to upgrade
years in advance because it's a very complicated thing. 

The other aspect is that the Navy, in executing and carrying out this
maintenance, has not had a good track record over the last decade. One
of the challenges they face is that the Navy has a limited number of
places where it can perform this kind of depot maintenance. The Navy
does this in what they call dry docks. There's a limited number, which
means it's very important for the Navy to accurately plan and execute
the length of the maintenance. Because when submarine A is in the dry
dock getting this maintenance, submarine B is waiting to come in to get
their maintenance done. So, if the first submarine is late and the
second submarine, 'oh, they can't get in.' And if they wait too long,
they lose that dive certification and they can't perform any missions.
So suddenly you have two subs unable to do what they want to do--one
because the delayed maintenance, one because it's waiting to get into
the dry dock. We found over the last 10 years, the Navy completed this
maintenance on time only 11% of the time.


[ Holly Hobbs: ]

Is it just getting harder to do?


[ Diana Maurer: ]

We found that in some respects it has gotten more difficult. But in
other respects the Navy has done better. So, the good news is the Navy
is doing a better job of estimating how long it takes to complete the
submarine maintenance. And that helps them with planning, helps them to
have a more predictable sense of when submarines are going to be
operationally available. So that's great. The challenge is they are
taking longer to actually complete this maintenance. So we found, for
example, in 2022, the Navy was completing this maintenance on average in
about 20 months for each sub. By 2025 that had increased to 33 months.
So that's a substantial increase. So that's a problem. 

The other problem that we found in our report is a relatively new one.
And that's a function of how the Navy has to deal with the older
submarines that it's going to retire from the fleet. Those submarines,
when they're at the end of their useful life, also have to go into these
dry docks. They also have to have their nuclear fuel taken off, the
reactor decommissioned. They have to be taken apart. Because there's a
limited number of these dry docks, those older submarines are now
waiting to get into their, into those dry docks for their own
decommissioning. That creates idle time because those subs also have a
crew aboard them.


[ Holly Hobbs: ]

What is idle time and what do we know about what's happening there?


[ Diana Maurer: ]

Our report talked about two different kinds of idle time. The first kind
is when you're talking about active submarines, submarines that are
waiting to go into the dry dock to get their scheduled maintenance.
They're going to come out and perform missions. We found that this
active idle time has actually been decreasing. So in 2022, it was about
1,500 or so days for the Navy, and that had decreased to less than 200
days by 2025. And that's because the Navy is doing better planning. But,
we found that this problem with inactive idle time has suddenly become a
major issue for the Navy. As recently as 2023, the Navy had almost 0
days of this inactive idle time. So older subs waiting to go into dry
docks to be decommissioned. But by 2025 that had increased to over 1,200
days. So that's a pretty big step up. And when you total all this
together, looking into the future, inactive idle time for the next 5
years, we project would be over 14,000 days. That's over $3.1 billion
for the cost of the crew, for the sailors, aboard these old submarines
that can no longer be used, that are just waiting to be decommissioned.


[ Holly Hobbs: ]

Is the Navy doing anything to address active idle time?


[ Diana Maurer: ]

So the Navy has definitely taken steps to address active idle time,
predominantly in improving their ability to plan how long it takes to
actually complete submarine maintenance. They've gotten better at doing
that, which is why we've seen active idle time decrease in recent years.


[ Holly Hobbs: ]

The other side of it is inactive idle time, and you mentioned that it's
millions of dollars for these things to be inactive and the sailors are
still working? 


[ Diana Maurer: ]

Correct? 


[ Holly Hobbs: ]

Why does the Navy need to crew inactive subs? 


[ Diana Maurer: ]

For the same reason they keep crews on the active subs. It's because
it's still a submarine, still has a nuclear reactor with nuclear fuel,
other sensitive material on it. So, they keep a crew aboard even the
subs they're planning to decommission. 

That inactive idle time, as I mentioned, is going to cost the Navy
billions of dollars. They are starting to think about what to do about
addressing this problem. So, in the course of our review, we found
different parts of the Navy. We're thinking about things like do we need
a full crew on a submarine that's going to go into a dry dock for
decommissioning? Or maybe we should extend the life of these older
submarines. 

If they stay operational longer then they'll go into decommissioning
later and there'll be less of a traffic jam in the relatively small
number of dry docks. Or maybe there are different ways. Maybe we don't
have to use just a dry dock. Maybe we can do some of this in terms of
what's pier side. So, the Navy is thinking about these things. But what
we found it was they had not done a specific analysis of the trade-offs,
the costs, the timeframes, the implications for safety for taking these
measures. So, we recommended that the Navy do a detailed analysis of all
these different options and then take action.


[ Holly Hobbs: ]

Last question, what's the bottom line of our report?


[ Diana Maurer: ]

Attack submarines are crucial for the U.S. Navy's ability to meet
national security needs. The Navy has done a better job of predicting
how long it takes to fix these subs, but are taking longer to repair the
subs they have, and they're facing a real problem in terms of getting
the older subs out of service and decommissioned. Addressing our
recommendations to the Navy will save them potentially billions of
dollars.


[ Holly Hobbs: ]

Thank you, Diana.


[ Diana Maurer: ]

Thank you.


[ Holly Hobbs: ]

And thank you for listening to the Watchdog Report. To hear more
podcasts, subscribe to us on Apple Podcasts, Spotify, or wherever you
listen. And make sure to leave a rating and review to let others know
about the work we're doing. For more from the congressional watchdog,
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