Aircraft?

There have been many rumours about confidential aircraft that may or may not have been developed or tested at Area 51. Although the main reason (of what we know) that Area 51 was to develop and test new aircraft during Cold War, these theories were not released in the documents by the Central Intelligence Agency in 2013.

TR-3A Black Manta

This is a rumoured project about a secret aircraft that people have been talking about for decades, though nobody actually knows what it is or the purpose of the aircraft. In 1993, a newsletter publisher named Steve Douglas published an image of a mysterious looking speculative aircraft, captured and enhanced from a video taken be him near White Sands, N.M. The Federation of American Scientists Web site describes it as a "subsonic stealthy reconnaissance aircraft" but little other information has emerged.

Aurora
In 1985, the "name" Aurora  was accidently leaked in an unclassified budget document, which depicted a ramjet-powered reconnaissance and strike aircraft capable at flying at great altitudes. And that could be deployed anywhere in the world in a matter of hours.

Brilliant Buzzard

This rumoured project was about a very large "mothership" that would hold small deployable aircrafts. These deployable aircrafts would probably be an UAV (Unmanned Aerial Vehicle). The UAV would deploy from the larger "mothership" while in mid-air.