The Aurora (supposedly called the SR-91 Aurora) is a possible surveillance aircraft. No one knows if it ever existed. Supposedly, it was meant for trying out hypersonic flight, or speeds above 5 times the speed of sound. The name "Aurora" was used for the aircraft because in 1985, it appeared on an American military funding list. It might have been to replace the SR-71 Blackbird.
In 1989, a man named Chris Gibson was working on an oil rig when he saw a KC-135 Stratotanker, two F-111 Aardvarks, and a triangle-shaped craft refueling. He did not know what it was. During 1991 in Southern California, there were a lot of sonic booms being heard. There was also a pulse coming out of the engine. The most recent sighting was in 2006.