Five years before Concorde’s first flight, another majestic supersonic aircraft took to the skies — and almost became the inspiration for an even faster passenger plane.
It was the XB-70 Valkyrie, an experimental plane developed for the US Air Force. Its inaugural flight — 60 years ago in September 1964 — kicked off a golden era for supersonic aircraft. The plane would later achieve a speed of just over 2,000 miles per hour, nearly 50% faster than Concorde.
“The overall design of the XB-70 was a thing of beauty,” says Tony Landis, a historian at the Air Force Materiel Command in Dayton, Ohio. “To think such an attractive aircraft, with its speed and altitude capabilities, was built over 65 years ago is hard to comprehend in today’s AI and computer-based engineering environment.”
The XB-70 program was not without problems: As a military plane, it was obsolete before it was even rolled out, and its short lifespan was marred by a tragic accident. Even regular flights had everyone on edge, as the aircraft’s components were all pushed to the limits.
However, its design has made it an icon of supersonic flight: “To this day, people stop and stare at the Valkyrie parked majestically at the National Museum of the United States Air Force, admiring its size and shape,” Landis says. “Most people ask if this is a new design, as they’ve never seen anything like it.”
Dead on arrival
The plane was born out of a competition between Boeing and North American Aviation, then a major aerospace manufacturer that was eventually chosen by the Air Force, in 1957, to develop a bomber capable of carrying nuclear weapons at Mach 2 and 60,000 feet of altitude.
However, the downing of an American U-2 spy plane over the Soviet Union in 1960 caused a shift from manned bombers to ballistic missiles, and in 1961 President Kennedy billed the upcoming XB-70 as having little chance of penetrating enemy defenses successfully. As a result, just as North American was starting to build the aircraft, the goal of the program shifted to high-speed flight research.
The first XB-70 — nicknamed Valkyrie following a naming contest — was rolled out in Palmdale, California, on May 11, 1964. With a wingspan of over 100 feet, six General Electric turbojet engines at the back, and 185 feet long, it was easily one of the most impressive planes ever built.
Among its distinctive features were wingtips that remained horizontal at subsonic speeds, but folded down once supersonic to reduce drag. Its main design elements, like the delta-shaped wings and the thin, long fuselage were replicated by both Concorde and its Soviet clone, the Tupolev Tu-144, which even sported two “canards” or winglets right behind the cockpit — just like the XB-70 — giving pilots more control at low speeds.
“Throughout the 1960s, both the military and civil sector put vast amounts of resources into developing a supersonic transport,” says Landis. “In the early stages, nearly every aircraft company based its initial design around the XB-70.”
As more information became available, Landis adds, these designs morphed into more refined designs like Concorde, as well as other projects that remained on paper, such as the planned Concorde rivals imagined by Lockheed and Boeing.
Fake windows
Once it was clear that the Valkyrie’s role as a bomber was set aside, its designers came up with alternative uses for the plane: “North American engineers became very creative, with many different uses for the aircraft,” says Landis, “But the only variant to be given serious consideration was the transport version for military and civilian use.”
Three variations were proposed, ranging from a high-density one with capacity for 158 passengers, to a “deluxe” arrangement that allowed for 114 seats and included a lounge area in the center of the passenger compartment.
“While the first XB-70 was back at Palmdale for inspections and upgrades, North American took the opportunity to add fake window markings to one side of the aircraft to assist in the marketing of the transport variant. The windows were removed prior to the aircraft’s return to flight testing,” Landis says.
It’s hard to imagine what the passenger experience could have been like on such a plane, but according to Landis it would have been a lot like Concorde: “Smooth, quiet, with ample space between the seats. Due to the expense in operating the aircraft and limited seating, the cost would most likely be affordable only to the upper middle class and the wealthy.”
Most importantly, it would have been fast, connecting London and New York in just two and a half hours, compared to Concorde’s typical three and a half.
Other proposed versions of the plane imagined it as a launch platform for orbital spacecraft and even Minuteman missiles – but just like the passenger version, these never materialized.
A fatal crash
The XB-70 program was further cut short by a fatal accident that occurred in 1966, during a photoshoot organized by General Electric. The second, and more advanced, of the two existing Valkyries collided in midair with a smaller plane, an F-104N, killing its pilot as well as one of the XB-70’s own pilots, with the other surviving with serious injuries.
The destroyed Valkyrie had logged just 46 flights, and the remaining one ended its career after 83 flights — many of which with NASA as a supersonic testbed — and just over 160 hours in the air.
The very last of those flights occurred on February 4, 1969, to ferry the plane from what is now NASA’s Armstrong Flight Research Center in California to Wright-Patterson Air Force Base in Ohio, where the aircraft joined the collection of the Air Force Museum.
While the program may not have lived up to its full potential, the XB-70’s legacy still stands, Landis says: “All large, high-speed aircraft designs benefit from the work done by the XB-70. And the data from those research flights continues to affect the design of future aircraft.”