Fransico Julius, (left), a tour guide, shows U.S. Navy Sailors from the Nimitz Class Aircraft Carrier USS DWIGHT D. EISENHOWER (CVN 69) photos of how the historic city of Rome looked like thousands of years ago during their visit in Italy on Oct. 19, 2006. EISENHOWER is on a for a four-day port visit in Naples, Italy. (U.S. Navy photo by Mass Communication SPECIALIST 3rd Class Matthew D. Leistikow) (Released)

Aircraft carriers are warships that act as airbases for carrier-based aircraft. In the United States Navy, these consist of ships commissioned with hull classification symbols CV (aircraft carrier), CVA (attack aircraft carrier), CVB (large aircraft carrier), CVL (light aircraft carrier), CVN (aircraft carrier (nuclear propulsion) and CVAN (attack aircraft carrier (nuclear propulsion). The first aircraft carrier commissioned into the United States Navy was USS Langley (CV-1) on 20 March 1922.