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The Los Angeles-class fast-attack submarine Alexandria (SSN 757) departs the floating dry dock at Naval Base Point Loma on April 5.(U.S. Navy photo by Mass Communication Specialist 1st Class Thomas Gooley/Released)

WASHINGTON — The Navy earlier this month completed a service life extension for the Los Angeles-class submarine Alexandria (SSN-757), extending its life by three years out to September 2025, the service said this week.

Earlier this month the Navy said that the sub “undocked and departed the West-coast’s only U.S. Navy-operated floating dry-dock, ARCO (ARMD-5) April 5, following a seven-month maintenance period.”

That maintenance period also included the three-year service life extension, Naval Sea Systems Command, the agency responsible for managing the service’s submarine maintenance schedule, told Breaking Defense.

The Navy for several years now has been evaluating each of its Los Angeles-class submarines, which first entered the fleet in the 1970s, to determine if their service lives could be extended. The LA-class is the predecessor to the Virginia-class, which the Navy is continuing to build today.

Rear Adm. Jonathan Rucker, program executive officer for attack submarines, told reporters in November the LA-class Scranton (SSN-756) has also been approved for a life extension. A spokeswoman for NAVSEA told Breaking Defense on Wednesday that boat is slated to begin its maintenance period in the third quarter of fiscal 2023 and will result in the sub being operational through September 2026.

The Pentagon’s longstanding requirement for fast attack submarines is 66, a metric the Navy has struggled to hit. The most recent long-term shipbuilding plan indicated there are 50 subs in service today and, even in the most optimistic scenarios, that number won’t reach 66 until the early 2050s. That statistic combined with the fact submarines are one of the most sought-after assets for combatant commanders around the world makes each service life extension the Navy completes particularly valuable for the broader Pentagon.

Adding to the pressure to keep subs operating is AUKUS, the trilateral security pact between the United States, United Kingdom and Australia. In February, President Joe Biden announced the so-called “optimal pathway” for Australia to produce nuclear-powered submarines would include the US selling three or five Virginia-class boats as an interim capability, making it even more difficult for the US to reach its 66 sub goal.

Although the shipbuilding plan revealed that the Navy intends to replace the sold-off subs with more Virginia-class boats, the plan was blunt about the fact the full impact of the security agreement will have on Navy shipbuilding is unknown.

“The full impact of AUKUS upon the Navy’s shipbuilding plan cannot be characterized in this year’s report given the conclusion of the March 2023 trilateral agreement coincided with the finalization of this report coupled with additional studies that will continue this summer,” according to the shipbuilding report.