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Smart Bombs: Military, Defense and National Security

Meet the SR-91 Aurora: The Air Force’s Mach 5 Spy Plane Dream?

SR-71 Blackbird Spy Plane. Image Credit: Creative Commons.

Did the SR-91 Actually Exist? – In the 1980s, an idea was conceived by military planners to develop a hypersonic spy plane that could reach Mach 5+ (or five times the speed of sound), making it truly the fastest manned aircraft ever to fly. Although there is little evidence such an aircraft was actually built, more than a few aviation buffs have argued that it may have at least reached the prototype stage as the SR-91 Aurora.

The goal of the military’s program was to develop a replacement for the aging and expensive to maintain a fleet of SR-71 Blackbird reconnaissance, which cost around $200 – $300 million a year each to operate. Technically known as a Special Access Program (SAP) – a “black program” that isn’t generally for public knowledge – little has been released about the SR-91.

Even the name “Aurora” was only disclosed when censors failed to catch a reference to it in a 1985 budget request that also discussed the state of the SR-71 and U-2 programs, and potential replacements.

More recently, in May 2006, a British Ministry of Defence report referred to the U.S. Air Force’s priority plans to produce a supersonic vehicle that could reach speeds of Mach 4 to 6. That had led some to speculate that the report was another reference to the SR-91 – yet connecting the dots doesn’t actually reveal the full picture.

If the program did exist, it was likely canceled due to a shift from spy planes to high-tech unmanned aerial vehicles and reconnaissance satellites that can do the same job without risk to a human pilot.

As it stands, the evidence is thin, yet there have been reported sightings of advanced aircraft, yet that is hardly conclusive evidence.

SR-91 – Seeing Is Believing

One of the most lingering questions among aviation buffs is whether the military actually produced a prototype of the SR-91 Aurora. To date, there is almost no evidence to suggest it did.

According to, there have been a couple of unverified sightings of what may or may not have been an SR-91. The most “well-known instance” of a reported sighting occurred in August 1989. Oil-exploration engineer Chris Gibson claimed to have seen a “triangular-shaped” aircraft darting across the North Sea. In the years since it has been suggested that Gibson had seen the Aurora during the test flight.

However, other aviation experts have countered that it was more likely that he saw a B-2 Spirit – which certainly has a triangular shape and did in fact have its first flight earlier that year. An alternative suggestion is that the triangular-shaped aircraft was a Lockheed F-117 Nighthawk, which had been also been tested by the RAF in the late 1980s. Both seem plausible – certainly more plausible than the SR-91.

Looking At The Facts

According to Gibson’s account, the aircraft was moving at considerable speed but it is doubtful it was anywhere close to traveling at Mach 5, as it would have been hard to even determine its shape. There is also no reason to suggest why a prototype of a truly top-secret aircraft would even be flying slow enough and low enough to be witnessed over the North Sea.

The bigger issue is that the North Sea is a highly trafficked body of water, and one where Soviet aircraft, ships and even submarines regularly traveled through. No one tests the most advanced and top-secret platform where it can be easily witnessed!

The other issue is where such prototype aircraft could even take off from and then land? The North Sea isn’t exactly a remote body of water and while the UK has numerous air bases, they’re not generally used for top-secret tests.

Did the SR-91 Cause a Sky Quake?

About the only other notable “evidence” of the existence of the SR-91 is that “sky quakes” were reported to have been heard at times over Los Angeles. To some that is proof of the unseen Aurora traveling so fast it could be heard but not seen.

Yet, it was more likely that the sounds came from aircraft operating out of Groom Lake (aka Area 51) in Nevada, and there remains little evidence to suggest it was the Aurora.

Of course, there is a model kit version, but what is actually based on is anyone’s guess.

Now a Senior Editor for 1945, Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers and websites. He regularly writes about military hardware, and is the author of several books on military headgear including A Gallery of Military Headdress, which is available on Peter is also a Contributing Writer for Forbes.

Written By

Expert Biography: A Senior Editor for 1945, Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers, and websites with over 3,000 published pieces over a twenty-year career in journalism. He regularly writes about military hardware, firearms history, cybersecurity, and international affairs. Peter is also a Contributing Writer for Forbes. You can follow him on Twitter: @PeterSuciu.