A black project is a term used for a highly classified military or defense project publicly unacknowledged by government, military personnel, and contractors. Examples of United States military aircraft developed as black projects include the F-117 Nighthawk stealth attack aircraft and the B-2 Spirit stealth bomber, both of which were highly classified and denied as existing until ready to be announced to the public. In the United States, the formal term for a black project is Special access program (SAP). The money that funds these projects is referred to as the black budget.
Speculated or classified