In generic use, an experimental aircraft is an aircraft that has not yet been fully proven in flight. Often, this implies that new aerospace technologies are being teste on the aircraft, though the label is more broad. Experimental aircraft is also a specific term referring to an aircraft flown with an experimental category Airworthiness Certificate. The term experimental aircraft is often erroneously used to mean homebuilt aircraft. While most homebuilt aircraft are registered as experimental category aircraft in the U.S., there are many types of experimental aircraft that are not homebuilt.