For 40 years Huntington Ingalls Industries (HII) has been the sole builder of the US Navy's nuclear aircraft carriers. Rivaling nuclear submarine builder General Dynamics, HII is the largest naval shipbuilder in the world; it also maintains, refuels, and repairs nuclear aircraft carriers and submarines. In addition, HII supplies expeditionary warfare ships, surface combatants, submarines, commercial oil hull tankers, and Coast Guard surface ships, as well as provides aftermarket fleet support. Almost off its offerings are sold to the US government.