Aircraft carriers

An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and facilities for carrying, arming, deploying, and recovering aircraft. Typically, it is the capital ship of a fleet, as it allows a naval force to project air power worldwide without depending on local bases for staging aircraft operations. Aircraft carriers are expensive to build and are critical assets. Carriers have evolved since their inception in the early twentieth century from wooden vessels used to deploy balloons to nuclear-powered warships that carry numerous fighter planes, strike aircraft, helicopters, and other types of aircraft.

There is no single definition of an "aircraft carrier," and modern navies use several variants of the type. These variants are sometimes categorized as sub-types of aircraft carriers, and sometimes as distinct types of naval aviation-capable ships. Aircraft carriers may be classified according to the type of aircraft they carry and their operational assignments. Admiral Sir Mark Stanhope, former head of the Royal Navy, has said, "To put it simply, countries that aspire to strategic international influence have aircraft carriers".

As of 30 January 2017, there are thirty-seven active aircraft carriers in the world within twelve navies. The United States Navy has 10 large nuclear-powered carriers (known as supercarriers, carrying up to 90 aircraft each), the largest carriers in the world; the total combined deckspace is over twice that of all other nations combined. As well as the supercarrier fleet, the US Navy has nine amphibious assault ships used primarily for helicopters (sometimes called helicopter carriers); these can also carry up to 25 vertical or short take-off and landing (V/STOL) fighter jets, and in some cases, are as large as some other nations' fixed-wing carriers.

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