Aircraft carriers are large naval vessels that serve as mobile airbases at sea, allowing aircraft to operate farther from shore. Early carriers in the 1910s and 1920s conducted experimental operations with seaplanes and fixed-wing aircraft. During World War II, over 40 aircraft carriers were commissioned by the US, though only 3 survived the war. Modern carriers are nuclear-powered and carry dozens of aircraft, with the largest super carriers displacing over 100,000 tons. Carriers come in various classes defined by their size and capabilities.