The world’s largest amphibious assault ships are the US Navy’s America-class vessels, which have a length of 257 m (844 ft) and a full-load displacement of 45,693 tonnes. The America-class vessels are built by US defence firm Northrop Grumman Shipbuilding, at a cost per unit of $10bn (£7.58bn). Their purpose is to deliver a large fighting force to enemy shores. Each vessel carries 12 Osprey tilt rotor aircraft, nine F-35B Lightning II joint strike fighters, four AH-1Z Viper attack helicopters, four CH-53K heavy cargo helicopters, two SH-60 Seahawk multi-role helicopters and 1,687 US Marines. There are currently three ships in the class, the first of which, USS America, entered service on 11 October 2014.
