The SR-91 Aurora, a reported successor to the SR-71 Blackbird spy aircraft, is conjecture with little proof of its existence. Though there was a rumor based on a budget code name and one supposed sighting in 1989, the program probably never passed the conceptual stage thanks to innovations in satellites and unmanned aerial vehicles. This theory continues to hold fast even as a series of intriguing incidents and observer reports have teased airplane buffs and defense experts for decades.
In August 1992, seismic signals detected by the United States Geological Survey along the San Gabriel Valley of Southern California indicated sonic booms from a supersonic plane flying high-altitude, happening repeatedly on Thursday mornings at 7 a.m. Jim Mori, a United States Geological Survey seismologist at Caltech, said in a 1992 interview with the LA Times, “It’s something that’s traveling through the atmosphere at several times the speed of sound in a generally northeasterly direction.”
The character of these reports added fuel to the flames of speculation that a top-secret plane, perhaps the elusive Aurora, was undergoing testing out of the secretive Groom Lake installation, more commonly referred to as Area 51. Interestingly, the Air Force denied them at the time.
Aviation Week and Space Technology, another credible aviation publication, also had an unexplained aircraft sighting at Beale Air Force Base, in northern California, flying in formation with two F-117 Nighthawks and a KC-135 refueling tanker. Witnesses described this aircraft as turning off its lights on the outside when it joined the formation, and its engine making a noise that sounded like “air rushing through a big tube.”
Furthermore, there were reports of unusual contrails, known as “doughnuts on a rope,” and linked to the Aurora program, indicating the application of a next-generation pulse detonation engine. But whether this technology is ever going to be feasible for hypersonic speeds is questionable.
The existence of the SR-91 Aurora was made even more complicated by U.K. sightings. In August of 1989, Chris Gibson, a qualified airfield observer, had sighted a triangle-shaped plane with two F-111s and a KC-135.
In 2006, respected aviation journalist Bill Sweetman decided that testimony from 20 years of searches into budget overruns, unidentified sonic booms, and the Gibson sighting validated the existence of the program in its early days.
