An HH-46 Sea Knight helicopter takes off as another stands on the flight deck aboard the nuclear-powered aircraft carrier USS NIMITZ (CVN-68). Both helicopters, part of the helicopter combat support squadron aboard the ammunition ship USS SHASTA (AE-33), are delivering supplies to the carrier during vertical replenishment operations between the two vessels. The NIMITZ is taking part in WestPac '93

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.