An aircraft carrier is a warship designed with a primary mission of deploying and recovering aircraft, acting as a seagoing airbase. Aircraft carriers thus allow a naval force to project air power worldwide without having to depend on local bases for staging aircraft operations. The Nimitz class aircraft carriers are the largest warships in the world, each designed for an approximately 50 year service life with one mid-life refueling. The NIMITZ-class carriers are a floating airport, capable of launching as many as four aircraft a minute. The ship's four catapults and four arresting gear engines enable her to launch and recover aircraft rapidly and simultaneously. The ships carry seven different types of aircraft with a total complement of more than 80 planes. During flight operations, the flight deck of 4.5 acres is a scene of intense activity, with crew, aircraft and other equipment functioning as a well-rehearsed and carefully choreographed team to ensure both efficiency and safety.