Three U.S. Navy littoral combat ships sail in formation in the eastern Pacific Ocean in 2019. The Navy’s current shipbuilding practices led to large cost overruns in building the ships, according to a government watchdog agency. (Shannon Renfroe)

The Navy must throw out its worn shipbuilding playbook if it wants to grow its fleet enough to meet critical national security needs, a congressional watchdog agency said.

The service’s deficient planning approach to designing, building and delivering ships has led to huge cost increases, delays in putting vessels into service and missed performance goals, the Government Accountability Office said in a report Tuesday.

The GAO noted that poor buying decisions are made worse by a budgeting process that requires the Navy to secure long-term funding before the full scope of a project is understood.

The Navy has about 296 numbered battle force ships, including aircraft carriers, destroyers, submarines and combat logistics vessels. But the service wants to see the fleet grow to 381 battle force ships over the next 30 years.

The report casts doubt on the Navy’s ability to achieve that goal unless its acquisition approach better aligns “with innovative practices that promote timely, predictable development and delivery of new, fully capable ships.”

To improve performance, the Navy should use proven ship design and product development practices rooted in the approaches of industry-leading companies, according to the report.

“Leading practices offer the Navy a near-term path toward restoring credibility with the operational fleet, Congress, and the taxpayers,” the report stated.

The GAO added that since 2015, the agency has made 90 recommendations identifying design practices used by commercial ship buyers and builders that the Navy can use.

Though the service has agreed to many of the recommendations, it has only fully or partially implemented about 30 of them, the GAO said.

Among the recommendations are using commercial shipping practices that ensure schedule, cost and requirements expectations are better informed.

The Navy currently sets those expectations when a ship’s design is unstable, or in progress, which results in insufficient information for decision-making. That raises the risk of higher costs and delays, the report stated.

Using the industry model would help the Navy avoid problems such as those that led to tens of billions of dollars in cost overruns to build the littoral combat ships and Zumwalt-class destroyers.

Beyond the added spending, the ambitious plan to add developmental technologies to the destroyers resulted in years of delays.

Ultimately, the Navy was forced to reduce the number of Zumwalt-class destroyers from 32 to just three, at a cost of $10.6 billion each, more than seven times the original estimate, the GAO said.

Meanwhile, the Navy determined that upgraded Arleigh Burke-class destroyers more effectively met changing mission needs, according to the report.

While the Navy has taken some actions toward improving shipbuilding outcomes, it isn’t apparent that the service has fully understood or applied lessons from previous mistakes, the GAO said.

Two newer programs — the Constellation-class frigate and the medium landing ship, or LSM — are experiencing similar problems, according to the agency.

The Navy began work on the first Constellation frigate in 2022 with a then-estimated price tag of $1.3 billion. But estimates have since ballooned by more than $200 million, and delivery of the ship has been delayed by three years to 2029, according to the report.

Using faulty metrics, the Navy determined that the design of the ship was nearly 88% complete as it awarded construction contracts. A later evaluation by the service showed that design progress was just 70% complete.

As a result, construction has stalled while the Navy and the shipbuilder negotiate important technical requirements, the GAO said.

Unrealistic design plans also have contributed to delays and likely higher costs for LSMs, which transport Marines and their supplies, the agency said.

The program is in the process of revising its cost estimates and timelines, the GAO said.