The X B Seventy Valkyrie, the Six-Engine Mach-Three Giant That Only Flew as Two, Lost One in a Photo Shoot, and Now Fills a Hangar in Dayton

The North American XB-70 Valkyrie was a six-engine, Mach-3 experimental bomber built in the late 1950s and early 1960s to fly higher and faster than any weapon could reach. Only two were ever built; one was destroyed in a mid-air collision during a June 8, 1966 photo shoot, and the sole survivor is now on display at the National Museum of the United States Air Force in Dayton, Ohio. Though it never entered service, the Valkyrie became one of the most important flying laboratories of the supersonic age.

What Was the XB-70 Valkyrie?

The Valkyrie was an aircraft the size of a passenger jet, painted bone white, with a long heron-beak nose and six engines buried in its belly. It was designed to cruise at Mach 3 - roughly 2,000 miles per hour, or three times the speed of sound - at an altitude of 70,000 feet.

The design logic of the mid-1950s was blunt. America’s frontline bombers, the subsonic B-52s, lumbered along too slowly to survive over a defended target. The reasoning was that a bomber flying high enough and fast enough could outrun any fighter or missile sent to stop it.

At Mach 3, air no longer slips over an airframe - it slams into it. Friction heats the skin until the leading edges run hotter than 300 degrees, well past the point where ordinary aluminum softens and fails.

How the Valkyrie Survived Mach-3 Heat

To handle that heat, North American Aviation built most of the aircraft from stainless steel, brazed into a honeycomb sandwich made of thousands of tiny cells. The result was a skin that was light, strong, and heat-resistant.

Nothing like it had been attempted at that scale. In effect, the company had to invent the manufacturing process at the same time it was building the airplane.

What Is Compression Lift?

The Valkyrie’s signature innovation was compression lift, sometimes described as the aircraft “riding its own shock wave.” At Mach 3, the nose and engine inlets throw off a cone of compressed air. On most aircraft, that shock wave is pure drag.

North American shaped the flat, wedge-like underside of the Valkyrie to trap that shock wave beneath the wing. The high pressure pushed up on the airframe and produced free lift - the airplane effectively surfed on its own thunderclap.

Why Did the Wingtips Fold Down?

Each wingtip - about six feet of wing per side - could hinge downward as much as 65 degrees in high-speed flight. This served two purposes.

First, dropping the tips helped pin the pressure wave under the wing so it couldn’t spill out the sides. Second, it shifted the aircraft’s balance to keep it stable at extreme speeds. With the tips lowered in flight, the Valkyrie had more folding wing area than many contemporary fighters had wing altogether.

The Engines and the Ground-Shaking Power

Six General Electric turbojets sat three-and-three in a box beneath the tail, each fed by variable inlet ramps. Together they moved a machine that weighed roughly a quarter of a million pounds fully loaded. Observers at Edwards Air Force Base described not hearing the Valkyrie so much as feeling it - a vibration that came up through the boots.

Why the XB-70 Was Obsolete Before It Flew

Air Vehicle One rolled out in 1964 in Palmdale, California, and first flew in September 1964. But the aircraft was already outdated, and the reason traces to an event four years earlier.

In 1960, pilot Francis Gary Powers was shot down over the Soviet Union in a high-flying U-2 spy plane by a surface-to-air missile. If a missile could reach a U-2, it could reach a Valkyrie. Altitude and speed were no longer a shield, and the future of bombing shifted to flying low, beneath enemy radar.

With its entire rationale gone, the program was cut back. There would be no fleet of Mach-3 bombers. Instead, the two aircraft already underway would be finished as research ships - flying laboratories to study sustained flight at three times the speed of sound, feeding knowledge into supersonic transport programs and future high-speed designs.

The June 8, 1966 Crash That Killed Two Men

Air Vehicle Two, the better of the pair thanks to an improved wing, could hold Mach 3 for extended stretches. On June 8, 1966, it was flying over the Mojave Desert when General Electric arranged a publicity photo shoot: a formation of aircraft, all powered by GE engines, tucked in tight around the white Valkyrie.

Flying close formation off the Valkyrie’s right side was an F-104 Starfighter flown by well-known NASA test pilot Joe Walker, a veteran who had flown the X-15 to the edge of space. What few appreciated that morning was that the Valkyrie’s folding wingtips trailed powerful, invisible wingtip vortices.

In the glare, holding tight position, Walker’s Starfighter drifted a few feet too close. The vortex flipped his aircraft over the top of the Valkyrie, shearing off both vertical tails before exploding. Walker was killed instantly.

The Valkyrie flew on briefly, then began to yaw and roll, fell into a flat spin, and went down. Copilot Carl Cross was killed. Pilot Al White managed to fire his escape capsule but was badly injured. Two aircraft and two men were lost - for a photograph.

The accident became a landmark lesson in wake turbulence and formation discipline. Every warning pilots receive today about staying clear of a heavy aircraft’s wingtip vortex traces in part to that morning over the Mojave.

Where Is the XB-70 Valkyrie Today?

After the crash, only Air Vehicle One remained. It flew research missions for about another year and a half before its final flight in early 1969, when it was flown to Wright-Patterson Air Force Base in Dayton, Ohio, to become a museum piece.

For years it sat outdoors, exposed to Ohio weather, but the museum eventually built an indoor, climate-controlled home. Restored to the way it looked the day it rolled out of Palmdale, it is now the only XB-70 left in the world, on display in the museum’s research and development gallery.

Why the Valkyrie Still Matters

By strict Pentagon accounting, the Valkyrie was a failure: billions spent, no operational aircraft, and a fatal crash. But everything learned building it - the stainless-steel honeycomb, the behavior of air at Mach 3, the heating and structural challenges, and the idea that a shock wave could be made to lift rather than drag - flowed directly into supersonic transport research and into the understanding of high-speed flight that followed.

It was, in the end, a teacher. It also stands as proof of nerve: a moment when engineers looked at a problem no one had solved and went out to the high desert and built the thing. The National Museum of the United States Air Force is free to visit, and the Valkyrie remains one of the great sights in all of aviation.

Key Takeaways

• The XB-70 Valkyrie was a six-engine, Mach-3 experimental bomber designed to cruise at 70,000 feet; only two were ever built.
• Its innovations included a stainless-steel honeycomb structure, compression lift (“riding its own shock wave”), and wingtips that folded down as much as 65 degrees in flight.
• The program was rendered obsolete by surface-to-air missiles after Francis Gary Powers’ U-2 was shot down in 1960, and was converted into a research effort.
• On June 8, 1966, an F-104 flown by NASA pilot Joe Walker hit a wingtip vortex and collided with Air Vehicle Two, killing Walker and copilot Carl Cross and producing a lasting lesson in wake turbulence.
• The surviving aircraft, Air Vehicle One, made its final flight in early 1969 and is displayed today at the National Museum of the United States Air Force in Dayton, Ohio - the only XB-70 left in the world.