The North American XB-70 Valkyrie, the Six-Engine Mach Three Bomber That Outlived Its Own Mission and Now Fills a Hangar in Dayton

The North American XB-70 Valkyrie was a six-engine bomber designed to cruise at Mach 3 and 70,000 feet, fast and high enough to fly over Soviet defenses untouched. It was rendered obsolete before it entered service by surface-to-air missiles, and only two were ever built. One was destroyed in a 1966 midair collision; the survivor, Air Vehicle Number One, sits in the research and development gallery of the National Museum of the United States Air Force in Dayton, Ohio, where it has remained since 1969.

What Was the XB-70 Valkyrie?

In the 1950s, the strategy behind American bombers was simple and unforgiving: fly high, fly fast, and cross the target before enemy fighters could climb up to meet you. The B-52 was the workhorse, but the Air Force wanted something that would make Soviet air defenses irrelevant altogether.

The requirement was staggering. Not climb to 70,000 feet, but cruise there - sustained, for hours - at three times the speed of sound, roughly 2,000 mph, while carrying a nuclear payload. That is an airliner-sized aircraft operating at a speed where the air itself begins to fight back.

North American Aviation won the contract. This was the same company behind the P-51 Mustang, the F-86 Sabre, and the X-15 rocket plane. The airplane they built still looks like it belongs to another planet: brilliant white, nearly the length of a football field, with a needle nose and twin rudders mounted high on the tail.

How Did the Valkyrie Fly at Mach 3?

At Mach 3, the air piles up in front of the aircraft and forms a shock wave - essentially wasted energy and drag. North American’s engineers turned that problem into an advantage with a principle called compression lift.

Instead of fighting the shock wave, the Valkyrie rode it. The underside of the aircraft was shaped, and the wingtips were hinged to fold down as much as 65 degrees in flight, trapping the aircraft’s own shock wave beneath it like a surfer riding his own wave. That trapped pressure produced free lift. Each folding wing panel was larger than the entire wing of a fighter jet, and no aircraft has really done this since.

The heat was the other great obstacle. At Mach 3, air friction heats the skin to 200 to 300 degrees and beyond, temperatures that soften ordinary aluminum. So most of the airframe was built from stainless steel in a brazed honeycomb sandwich - cutting-edge metalwork that had to be invented as the program went. Panels frequently came out of the oven improperly bonded.

Power came from six General Electric YJ93 engines, each producing around 30,000 pounds of thrust in afterburner. They were clustered in a box beneath the fuselage and fed by a large rectangular intake whose internal ramps and doors had to slow incoming air from supersonic to subsonic before it reached the engines. Early planners even explored a toxic, high-energy boron “zip fuel,” but abandoned it; the Valkyrie flew on a special jet fuel blend, which it consumed by the ton.

The Two Aircraft and Their Performance

The first aircraft, Air Vehicle One, rolled out in May 1964 and flew that September. Troubles appeared immediately - a main gear that hung up on the first flight, and pieces of honeycomb skin peeling off the wings at speed. It did not reach Mach 3 until October 1965, and even then could hold that speed only a few minutes before heat began tearing at the airframe.

Air Vehicle Two was the refined machine. Engineers added more droop to the wing and corrected the geometry, and it could genuinely sustain Mach 3. In May 1966, it cruised at Mach 3 for 32 minutes straight at 72,000 feet - the airplane doing exactly what the original dream had promised.

Why Was the Valkyrie Cancelled?

The world changed underneath it. While North American was perfecting stainless steel, the Soviets were building surface-to-air missiles - and a missile does not care how high or how fast you fly. In 1960, Soviet missiles downed a U-2 spy plane at 70,000 feet. Altitude was no longer protection; it was a target.

The entire rationale for the Valkyrie collapsed. Strategists decided the next bomber would go the opposite direction - low, under the radar, hugging the terrain. The bomber program was cancelled in 1961. The two aircraft already committed to were completed and handed over to research, becoming flying laboratories for NASA and the Air Force. They studied supersonic transport, making the XB-70 the closest thing America ever had to a full-scale supersonic airliner test bed.

The June 8, 1966 Crash

On June 8, 1966, General Electric arranged a publicity photograph - a formation of aircraft powered by GE engines tucked in tight around the white Valkyrie. Air Vehicle Two, the aircraft that could hold Mach 3, led the formation. Around it flew an F-4 Phantom, an F-5, a T-38, and off the right wing, an F-104 Starfighter.

The Starfighter was flown by Joe Walker, NASA’s chief test pilot, a man who had flown the X-15 to over 300,000 feet and one of the finest aviators the country ever produced.

The photograph was taken. Then something went wrong. The prevailing theory is that Walker’s F-104 was caught in the wingtip vortex spinning off the Valkyrie’s huge drooped wing. It rolled him into the bomber. The Starfighter came up and over, sheared off both of the Valkyrie’s vertical tails, and exploded. Joe Walker was killed instantly.

The Valkyrie flew on straight and level for a few seconds with no tails at all, then yawed into a flat spin and came down in the desert. Test pilot Al White ejected in the escape capsule and survived, badly injured. His copilot, Air Force Major Carl Cross, was on his first flight in the aircraft; he never got out.

Two lives and the better of the only two Valkyries were lost in seconds - and none of it was necessary. No test point was being flown and no data was being gathered. It was a photo formation. That is why aviators still study this accident when they talk about formation discipline, responsibility for separation, and the difference between a mission and a stunt.

The Last Valkyrie in Dayton

That left Air Vehicle One - the first aircraft, the one that could never quite hold Mach 3, with its flatter wing and all its early troubles. It flew research missions for two more years. Then, in February 1969, it made one final flight, from California to Wright-Patterson Air Force Base in Ohio, and it has not moved since.

What stands in the museum gallery today is the only one left - not one of a fleet, but the last of a species that numbered exactly two. Nearly 90 feet of forward fuselage stretches out before you reach the wing. The folding wingtips are locked in the up position; imagine them drooping 65 degrees at 70,000 feet in air thin enough and hot enough to glow. Six engine exhausts cluster beneath the tail - all six once lit in afterburner with a sound crews said you could feel in your chest from a mile away.

It is indoors now, climate-controlled and roped off, because after the crash and the program’s death, someone recognized the aircraft was too important to let rust in a boneyard.

The Valkyrie never dropped a bomb or flew a mission that mattered to any war. By cold accounting, it was a failure: billions of dollars, two airplanes, one destroyed for a snapshot. But it was also the moment American engineers took on the hardest problem in flight - steel they didn’t yet know how to make, a wing that folded in the air, a shock wave trapped on purpose - and built it anyway. Much of what the country learned about supersonic transport, high-temperature structures, and large aircraft at extreme speed traces back to those two white ships and the men who flew them. It was simply an airplane that arrived at the party right as the music changed.

Key Takeaways

The XB-70 Valkyrie was a Mach 3, 70,000-foot bomber built by North American Aviation; only two were ever built.
It used compression lift and wingtips that folded down 65 degrees in flight, powered by six GE YJ93 engines, with an airframe built largely from stainless steel honeycomb to survive extreme heat.
The bomber program was cancelled in 1961 after surface-to-air missiles - proven by the 1960 U-2 shootdown - made high-altitude flight a liability rather than protection.
Air Vehicle Two was destroyed in a June 8, 1966 midair collision during a publicity photo shoot, killing NASA pilot Joe Walker and Air Force Major Carl Cross.
The surviving Air Vehicle One has been on display at the National Museum of the United States Air Force in Dayton, Ohio, since 1969.