A Special Certificate of Airworthiness (C of a) is a specific type of FAA-issued document that allows an aircraft to operate even if it does not meet the standard requirements for a "Normal" category aircraft. While a Standard C of a is for mass-produced planes used for transport or general flight, a Special C of a is issued for specific purposes. These categories include "Experimental," "Restricted," "Limited," or "Light-Sport." For instance, an Experimental certificate might be given to a home-built aircraft or a plane used for research and development. A "Restricted" certificate might apply to a plane modified for crop dusting or forest fire fighting. These certificates come with very specific operating limitations—such as staying away from densely populated areas—to ensure safety while allowing the aircraft to perform its unique mission.