U.S. Unmanned Aerial Systems: Congressional Research Service, January 3, 2012

Unmanned aerial systems comprise a rapidly growing portion of the military budget, and have been a long-term interest of Congress. Unmanned aircraft are commonly called unmanned aerial vehicles (UAVs), and when combined with ground control stations and data links, form UAS, or unmanned aerial systems. The use of UAS in conflicts such as Kosovo, Iraq, and Afghanistan, and humanitarian relief operations such as Haiti, revealed the advantages and disadvantages provided by unmanned aircraft. Long considered experimental in military operations, UAS are now making national headlines as they are used in ways normally reserved for manned aircraft.