The XB-70 Valkyrie, the Six-Engine Mach Three Bomber That Folded Its Wingtips in Flight and Now Sits Alone at Dayton After a Camera Killed Her Sister

SUMMARY: The XB-70 Valkyrie was a Mach 3 bomber that folded its wingtips in flight; the sole survivor sits in Dayton, Ohio.

The North American XB-70 Valkyrie was a six-engine, Mach 3 experimental bomber built in the late 1950s and early 1960s to cruise at 70,000 feet and outrun any defense. Only two were ever built, and only one survives today at the National Museum of the United States Air Force at Wright-Patterson Air Force Base in Dayton, Ohio. The program collapsed when surface-to-air missiles made high-and-fast bombers obsolete, and the better of the two aircraft was destroyed in a 1966 mid-air collision during a photo shoot.

What Was the XB-70 Valkyrie?

The Valkyrie was an enormous white aircraft - 185 feet long, built from stainless steel and titanium, and standing on landing gear tall enough to walk under without ducking. It was designed to be the fastest bomber in the world: a nuclear-strike platform that would fly so high and so fast that nothing could catch it.

It was conceived in the mid-1950s at the height of the Cold War. The Air Force’s frontline bomber, the subsonic Boeing B-52 Stratofortress, relied on reaching its target and returning intact. The doctrine of the day was simple - fly high, fly fast, stay untouchable. The Valkyrie was meant to take that idea to its absolute limit.

Why Was the XB-70 So Hard to Build?

The Air Force asked American industry for something close to impossible: a bomber that could hold Mach 3 - roughly 2,000 mph, three times the speed of sound - not in a brief dash but for hours at a time, all the way to a target.

At that speed, air doesn’t slip smoothly around an aircraft. It piles up, compresses, and heats. The Valkyrie’s skin would ride at over 500 degrees Fahrenheit for the entire cruise. Ordinary aluminum would soften and fail at those temperatures, so North American Aviation in California had to learn to build a large aircraft from stainless steel and titanium, brazed into a honeycomb sandwich - a technique nobody had mastered at that scale.

Engineers invented the tooling as they went. They would braze a panel, cut it open, and find the honeycomb hadn’t bonded, then start again. It took years just to figure out how to make the skin.

How Did the XB-70’s Engines and Air Inlets Work?

The Valkyrie was powered by six General Electric turbojets, bundled together in a large box beneath the rear fuselage. Each produced around 30,000 pounds of thrust in afterburner.

All six engines breathed through a single enormous shared inlet at the front, split down the middle by a knife-edge wall. Moving ramps inside the inlet slowed the incoming supersonic air before it reached the compressor faces. The inlet was a precision machine in its own right - get it wrong, and an engine could “unstart” with a bang like a cannon.

What Was Compression Lift and the Folding Wingtips?

The Valkyrie’s most brilliant feature was the way it used its own shockwave. At Mach 3, an aircraft drags a cone of compressed air beneath it, and normally that shockwave is just drag - a penalty. The Valkyrie was designed to ride on it.

The underside was shaped like a shelf, and the outer panels of the big delta wing were hinged to fold down in flight. On the ground, the wingtips stuck straight out. Accelerating through the sound barrier, the pilot drooped them down - as much as 65 degrees, nearly pointing at the ground.

This did two things. It trapped the shockwave under the wing so the aircraft could surf on the pressure it generated - a phenomenon called compression lift, and it was essentially free. Folding the tips also shifted the aircraft’s balance so it stayed stable in the thin air of the stratosphere. No full-size aircraft had ever done this, and none has done it since.

When Did the XB-70 First Fly, and How Fast Did It Go?

Ship number one, the first of the two aircraft built, made its first flight in September 1964. It was a handful early on - a main gear tire came apart on that first flight, and later the aircraft shed pieces of its folding wingtip in flight yet still flew home.

Ship one was never a clean Mach 3 machine. It had plumbing problems and a wing not built to the final specification, and it topped out around Mach 2.5.

Ship number two was the one that delivered. It had the wing built correctly, with the proper dihedral twist, and in the spring of 1966 it held Mach 3 for over half an hour at more than 70,000 feet. It proved the concept the whole program had been built to test.

Why Was the XB-70 Program Cancelled?

The world changed before the Valkyrie ever worked. The entire premise - fly so high and fast that nothing can reach you - had already been disproven. In May 1960, pilot Francis Gary Powers was flying a U-2 spy plane over the Soviet Union, higher than a B-52, when a Soviet surface-to-air missile knocked him out of the sky.

That was the answer to the whole question. A missile doesn’t care how fast the target is going. Altitude and speed were no longer a shield, and the mission the Valkyrie was born for was obsolete before it ever reached Mach 3. The bomber program was cancelled, and the two aircraft were handed over as research ships, studying sustained high-speed flight - data that fed into supersonic transport studies and NASA’s high-speed research.

What Happened to the Second XB-70?

On June 8, 1966, General Electric wanted a promotional photograph: five aircraft powered by GE engines flown in tight formation, with the good Valkyrie, ship number two, as the centerpiece. In the cockpit were Al White, North American’s chief test pilot, and Carl Cross, an Air Force major on his very first flight in the aircraft.

They formed up over the high desert near Edwards. Tucked in close off the Valkyrie’s drooped right wingtip was a Lockheed F-104 Starfighter, flown by Joe Walker, one of the finest research pilots alive - a man who had flown the X-15 to the edge of space.

A large delta wing sheds a powerful vortex off its tip. As best anyone can tell, the Starfighter got caught in that flow or drifted a hair too close. It rolled up and over the top of the Valkyrie, shearing off both vertical tails and raking across the left wing before exploding. Joe Walker was killed instantly.

The Valkyrie flew on for a few seconds with no tails, wings level, then yawed, rolled off, and fell into a flat spin. Al White ejected in his clamshell escape capsule and survived, badly hurt. Carl Cross never got out and rode the aircraft down. Two men died, and the best of the two Valkyries was destroyed - all for a photograph nobody needed.

Where Is the XB-70 Valkyrie Today?

The aircraft on display in Dayton is ship number one - the early one with the plumbing troubles that never made a clean Mach 3. After ship two was lost, ship one kept flying research missions for another two years. In February 1969 it was flown from California to Wright-Patterson and rolled into the museum, where it has remained ever since.

It is the only XB-70 Valkyrie left on Earth. It sits with its wingtips locked straight out, the way they were for takeoff, a monument to a future aviation imagined but never built. For one brief moment in the 1960s, engineers believed the airliners of tomorrow would cruise at Mach 3, and the Valkyrie was the proof of concept. The economics never closed, and the missile beat the altitude.

Key Takeaways

The XB-70 Valkyrie was a six-engine experimental bomber designed to cruise at Mach 3 and 70,000 feet, built from stainless steel and titanium to survive skin temperatures over 500°F.
Its hinged wingtips folded down as much as 65 degrees in flight to generate compression lift, letting the aircraft ride on its own shockwave - a feat never repeated on a full-size aircraft.
Only two were built; ship two achieved sustained Mach 3 flight in 1966 but was destroyed in a mid-air collision with an F-104 on June 8, 1966, killing pilots Joe Walker and Carl Cross.
The program was cancelled because surface-to-air missiles - demonstrated by the 1960 shootdown of Francis Gary Powers’ U-2 - made high-altitude bombers obsolete.
The sole survivor, ship one, has been on display at the National Museum of the United States Air Force in Dayton, Ohio since February 1969.