payloads. In 2013, the US Navy completed the first successful catapult launch and arrested landing of an unmanned aerial vehicle (UAV) aboard an aircraft carrier. After a decade of research and planning, the US Navy has been testing the integration of UAVs with carrier-based forces since 2013, using the experimental Northrop Grumman X-47B, and is working to procure a fleet of carrier-based UAVs, referred to as the Unmanned Carrier Launched Airborne Surveillance and Strike (UCLASS) system. Roles Naval aviation forces primarily perform naval roles at sea. However, they are also used for other tasks which vary between states. Common roles for such forces include: Fleet air defense Carrier-based naval aviation provides a country's seagoing forces with air cover over areas that may not be reachable by land-based aircraft, giving them a considerable advantage over navies composed primarily of surface combatants. Strategic projection Naval aviation also provides countries with the opportunity to deploy military aircraft over land and sea, without the need for air bases on land. Mine countermeasures Aircraft may be used to conduct naval mine clearance, the aircraft tows a sled through the water but is itself at a significant distance from the water, hopefully putting itself out of harm's way. Aircraft include the MH-53E and AW101. Anti-surface warfare Aircraft operated by navies are also used in the anti-surface warfare (ASUW or ASuW) role, to attack enemy ships and other, surface combatants. This is generally conducted using air-launched anti-ship missiles. Amphibious warfare Naval aviation is also used as part of amphibious warfare. Aircraft based on naval ships provide support to marines and other forces performing amphibious landings. Ship-based aircraft may also be used to support amphibious forces as they move inland. Maritime patrol Naval aircraft are used for various maritime patrol missions, such as reconnaissance, search and rescue, and maritime law enforcement. Vertical replenishment Vertical replenishment, or VERTREP is a method of supplying naval vessels at sea, by helicopter. This means moving cargo and supplies from supply ships to the flight decks of other naval vessels using naval helicopters. Anti-submarine warfare During the Cold War, the navies of NATO faced a significant threat from Soviet submarine forces, specifically Soviet Navy SSN and SSGN assets. This resulted in the development and deployment of light aircraft carriers with major anti-submarine warfare (ASW) capabilities by European NATO navies. One of the most effective weapons against submarines is the ASW helicopter, several of