Each U.S. aircraft carrier contains 50,000 tons or more of steel plate.  The USS Ronald Reagan, commissioned in 2003, used 70,000 tons of steel.

The steel for the Nimitz class of aircraft carriers must be able to withstand the impact of a 37-ton, F-14 Tomcat aircraft landing on the deck at 150mph, shield a ship’s crew from radiation generated by onboard nuclear reactors, and take the impact of shells and other projectiles.

The nuclear propulsion systems of aircraft carriers (and submarines) require nuclear-grade plate for reactor vessels, steam generators, and pressurizers.

The control cables on almost all aircraft, including fighter jets and military transport planes, are made from steel wire rope.  These machines could not remain in controlled flight without steel wire rope.

Source: American Iron & Steel Institute