US Navy (USN) Damage Controlman Second Class (DC2) Ronnie Longoria uses a Portable Exothermic Cutting Unit (PECU) during a damage control training exercise aboard the USN Aircraft Carrier, USS NIMITZ (CVN 68). The PECU provides for more rapid access into areas of the ship where normal access is impaired during firefighting operations. It is also used to drain accumulated firefighting water from areas of the ship where the effects of the accumulated water will impair the ship's stability

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.