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Mach 6 Mystery: Did the SR-91 Aurora Become the SR-72 Son of Blackbird?

SR-91 Aurora. Image Credit: Rodrigo Avella

Enigmatic SR-91 Aurora Still Turning Heads: It’s an interesting parlor game in defense analyst circles to ponder airplanes that could have been champions in the air. Sometimes these aircraft are real head-scratchers and seem like good ideas but continue to be enigmatic. Such is the case with the SR-91 Aurora spy plane that presumably was developed in the 1990s but likely never made it past the drawing board.

Lets’ take a look at the Aurora, an airplane that might have changed the way we view ultra-fast reconnaissance airplanes.

SR-91: Could There Be Something Better Than SR-71 Blackbird?

Toward the end of the Cold War, during the Reagan era, the Pentagon was looking for something faster and cheaper to fly than the SR-71 Blackbird. Air Force planners wanted a spy plane that could fly at hypersonic speeds (above MACH 5) and reach unheard of altitudes to stymie enemy air defense systems. This airplane was thought to have a triangle shape for stealth capabilities to confuse radar.

SR-71 Aurora Is Deep and Dark

This airplane was part of a special access program or “black” project, and little is known about it.

Speculation began in 1986 in an FY87 budget document when a line item for the word “Aurora” was funded for $2.3 billion. This was a significant appropriation that got tongues wagging. What exactly was the Aurora? There just weren’t any details of what was going on with that kind of funding.

Did the British Know Something That We Didn’t Know?

The mystery deepened over the following decades. But in 2006, there was another clue. The British Ministry of Defence penned a document that referred to an American hypersonic airplane that could reach MACH 4 to MACH 6. This may have been a reference to the Aurora.

SR-91: An Eye-Witness Could Have Seen Other Airplanes

Still, these were only details on paper and not much evidence beyond vaporware.

There was a sighting of a triangular-shaped airplane flying in 1989 that appeared to be something that wasn’t previously part of the Air Force fleet. An oil services engineer named Chris Gibson saw what he thought was a newfangled spy plane that year.

However, this could have been a B-2 Spirit or an F-117 Nighthawk, or even a figment of Gibson’s imagination because the airplane would not likely have flown that slow or low to be seen.

Would the Aurora Have Caused a Sky Quake?

Others have noted the ominous-sounding “sky quakes” heard in Los Angeles in the early 1990s. These booming noises were thought to be aircraft high-tailing at Groom Lake base in the Nevada desert, otherwise known as Area 51.


SR-91 Aurora. Image is an Artist Rendering. Image Credit: Creative Commons.

SR-91 Aurora

SR-91 Aurora. Image Credit: Creative Commons.

The Name of a Concept

The most plausible scenario with the Aurora is that it probably was a concept that was funded for research and development only. This could have been just a “hypothesis.” In other words, yes the United States was looking at successor airplanes to the SR-71 and U-2, and yes they were happy to throw some money at engineers and designers who were musing at the next-generation spy plane.

What came of this was not the Aurora, but most likely efforts to create the SR-72 “Son of Blackbird” program. This is also a hypersonic and high-flying spy plane. The SR-72 should start flying in sometime in the mid-2020s and is rumored to be gearing towards flying at Mach 6. The Aurora thus was likely a code name for a catch-all project that covered new spy plane development rather than an actual airplane.


SR-72, maybe. Screenshot from Top Gun 2 Trailer.

SR-72 Darkstar

SR-72 Darkstar. Image: Lockheed Martin.

Either way, it is interesting to discuss how the Aurora lived in many people’s imagination of airplanes flying at outrageous heights and speeds.

Now serving as 1945’s Defense and National Security Editor, Brent M. Eastwood, PhD, is the author of Humans, Machines, and Data: Future Trends in Warfare. He is an Emerging Threats expert and former U.S. Army Infantry officer. You can follow him on Twitter @BMEastwood.

Written By

Now serving as 1945s New Defense and National Security Editor, Brent M. Eastwood, PhD, is the author of Humans, Machines, and Data: Future Trends in Warfare. He is an Emerging Threats expert and former U.S. Army Infantry officer.