The cost-plus-fixed fee contract for life-cycle engineering and support services on the USS San Antonio class ships is worth $47 million.
The base contract, awarded in February, has a potential value of $249.4 million, the company said.
"This is an important option because it allows our broad range of post-delivery support to continue on these complex amphibious ships," said Doug Lounsberry, LPD 17 program manager, Northrop Grumman Shipbuilding.
"Our commitment to quality in this shipbuilding program remains steadfast. Once these ships enter the fleet, the same commitment to quality must be maintained throughout these support service contracts to provide the men and women of our U.S. Navy and U.S Marine Corps the best possible product in defending freedom."
Northrop Grumman's contract services include post-delivery planning and engineering, systems integration and engineering support, research engineering, material support, fleet modernization program planning and supply chain management.
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