oil and product tankers and container and cargo ships for commercial customers, satisfying Jones Act requirements that ships carrying cargo between U.S. ports be built in U.S. shipyards. On December 31, 2020, backlog for our major ship construction programs and the scheduled final delivery date of ships currently in backlog were as follows: In addition to design and construction activities, our Marine Systems segment provides comprehensive post-delivery services to extend the service life of these and other Navy ships. NASSCO conducts full-service maintenance and surface- ship repair operations in Navy fleet concentration areas in San Diego, California; Norfolk, Virginia; Mayport, Florida; and Bremerton, Washington. Electric Boat provides submarine maintenance and modernization services in a variety of U.S. locations, and Bath Iron Works provides lifecycle support services for Navy surface ships in both U.S. and overseas ports. In support of allied navies, we offer program management, planning, engineering and design support for submarine and surface-ship construction programs. Revenue for the Marine Systems segment was 26% of our consolidated revenue in 2020, 23% in 2019 and 24% in 2018. Revenue by major products and services was as follows: Year Ended December 31 2020 2019 2018 Nuclear-powered submarines $ 6,938  $ 6,254  $ 5,712  Surface ships 2,055  1,912  1,872  Repair and other services 986  1,017  918  Total Marine Systems $ 9,979  $ 9,183  $ 8,502  8