The North American XB-Seventy Valkyrie, the Mach Three Bomber America Canceled Before It Flew a Mission, and the White Giant That Waits for You at the National Museum of the United States Air Force in Dayton

The North American XB-70 Valkyrie was built to do something no bomber had done before: cruise at Mach 3 - roughly 2,000 mph - at 70,000 feet, deliver a nuclear weapon on target, and outrun any Soviet interceptor on the return leg. The program flew, proved its performance claims, and was canceled before it could ever serve the role it was designed for. One of its two airframes still exists. You can walk alongside it today at the National Museum of the United States Air Force in Dayton, Ohio.

Why the Air Force Needed Something They Couldn’t Catch

The B-52 Stratofortress entered service in the early 1950s as the backbone of Strategic Air Command’s nuclear deterrent. It was a capable machine - intercontinental range, eight engines, a payload that could reach any point on earth. But it was subsonic, and the world it operated in was accelerating fast.

Soviet radar networks were expanding. Surface-to-air missile technology was advancing rapidly. The comfortable assumption that a high-altitude subsonic bomber could always penetrate enemy defenses was becoming harder to defend. Strategic Air Command posed a direct question to its engineers: build something they genuinely cannot catch.

North American Aviation won the development contract in 1958. The requirements were unambiguous: Mach 3 cruise, 70,000-foot operating altitude, nuclear payload delivery, and enough performance to exit the target area before Soviet defenses could mount a meaningful response.

The Engineering Problems Nobody Had Solved Yet

At Mach 3, aerodynamic friction heats an aircraft’s skin to approximately 600 degrees Fahrenheit in sustained cruise. Aluminum - the standard airframe material of the era - softens and loses structural integrity at those temperatures. North American built most of the Valkyrie’s structure from stainless steel honeycomb panels and titanium, using a brazing process that was largely new to American aerospace manufacturing.

Standard jet fuel would become dangerously volatile inside Mach 3 fuel tanks. The program required development of a new fuel, JP-6, with a higher flash point and better thermal stability. The six General Electric YJ93 engines, each producing around 28,000 pounds of thrust in afterburner, fed through inlets designed to manage supersonic shockwaves at the nose of the aircraft - compressing and slowing incoming air from supersonic to subsonic speed before it reached the compressor blades.

Getting that inlet geometry right across the full speed envelope, from takeoff roll to Mach 3 cruise, consumed years of wind tunnel time. The airplane that emerged was 196 feet long, with a delta wing spanning 65 feet from root to tip on each side.

How the XB-70 Rode Its Own Shockwave

The most technically elegant aspect of the XB-70’s design is also the least commonly discussed.

At Mach 3, the aircraft didn’t simply fly through the air - it generated a shockwave ahead of the enormous delta wing that trapped a high-pressure air mass beneath the wing’s lower surface. This phenomenon, called compression lift, provided extra lift without adding drag. The faster the aircraft flew, the more efficiently it generated that cushion below.

To enhance the effect, the wingtips were hinged. At supersonic speeds, the outer panels folded downward - up to 65 degrees - to better capture and contain the high-pressure air beneath the wing. The XB-70 was, in a precise engineering sense, surfing on the pressure wave it created.

Why McNamara Canceled It

Two prototypes were built. AV-1 made her first flight on September 21, 1964, at Palmdale, California. The flight test program confirmed the aircraft performed as advertised.

The problem wasn’t the airplane. It was the strategic environment it was built to operate in.

By the early 1960s, the Minuteman I intercontinental ballistic missile had entered service in 1962. A ballistic missile could deliver a warhead to Moscow in 30 minutes, required no crew, needed no recovery plan, and cost a fraction of a Mach 3 bomber program. Secretary of Defense Robert McNamara canceled the XB-70 production program in 1961. The two completed prototypes would continue as research aircraft. There would be no operational fleet.

The program had cost approximately $750 million per aircraft in 1965 dollars. No combat missions. No production run.

The June 8, 1966 Midair Collision

AV-2 - the second prototype, fitted with small canard surfaces near the nose for improved pitch handling at altitude - had reached Mach 3 in January 1966. By June, the research program was well into its productive phase.

On June 8, 1966, five aircraft powered by General Electric engines gathered in loose formation over the Mojave Desert for a company publicity photograph. The formation included the XB-70 AV-2, a Northrop T-38 Talon, a McDonnell F-4 Phantom, a Lockheed F-104 Starfighter, and a Northrop YF-5A. A Learjet photo ship circled below with cameras running.

Joe Walker was flying the F-104. He was not a junior pilot building hours - he was a NASA research pilot with thousands of hours in high-performance aircraft, a former unofficial altitude record holder who had flown the X-15 above 50 miles altitude.

After the photos were taken and the formation began to break up, Walker’s F-104 drifted into the wingtip vortex generated by the XB-70. The vortex rolled the F-104 inverted and into the Valkyrie’s right vertical tail assembly. Both vertical fins were sheared from the XB-70. The F-104 disintegrated. Joe Walker was killed instantly.

Without its vertical fins, AV-2 entered an uncontrolled roll. Colonel Al White, the aircraft commander, activated his escape capsule but struck part of the aircraft structure on the way out, sustaining serious injuries. He survived. Major Carl Cross, the co-pilot, never had time to use his capsule. He went down with the aircraft into the Mojave Desert.

Congressional hearings afterward raised pointed questions about whether a formation flight arranged for a publicity photograph was an appropriate risk for a one-of-a-kind research prototype with two crew aboard. Those questions, and the long silence that answered them, are part of this program’s record.

What the Research Program Accomplished

AV-1 kept flying after the loss of AV-2. NASA used the surviving prototype as a high-speed research platform, accumulating flight data on compression lift efficiency, inlet behavior, thermal loads, sonic boom characteristics, and the aerodynamics of large delta-wing aircraft operating at extreme altitude and speed.

That data fed directly into American supersonic transport studies of the late 1960s. It informed the engineering philosophy behind what was simultaneously being developed in Europe as the Concorde. The knowledge base the XB-70 generated has influenced high-speed design programs in some measure ever since.

Joe Walker and Carl Cross paid for part of that knowledge. That is worth stating plainly.

AV-1 flew her last mission on February 4, 1969. She then flew herself from Edwards Air Force Base to Wright-Patterson Air Force Base in Ohio in April 1969, landing there for the final time before her transfer to the museum.

Seeing the XB-70 in Dayton

The National Museum of the United States Air Force at Wright-Patterson is free to visit. It spans four hangars and covers the full arc of powered flight. AV-1 is in the Research and Development Gallery - the same building as the B-2 Spirit stealth bomber and the SR-71 Blackbird.

The aircraft is too large to look right indoors. That registers immediately. 196 feet of airplane inside a building is a surreal object. The delta wing extends 65 feet on each side. The nose, designed to cut through the Mach 3 bow shockwave, angles toward the gallery entrance as though reading the door for a gap it could fit through. The six engine exhausts at the tail are large enough to stand inside.

The white paint has yellowed in places. The stainless steel honeycomb panels the engineers brazed together to handle 600-degree friction heat are right where they have always been. You can walk the full length of the aircraft, stand beneath the delta wing, and consider what it took to build this machine in 1964 - with slide rules, wind tunnel models, and manufacturing processes that had to be invented as the work proceeded.

Some look at this program and see a failure: a canceled contract, a machine that never flew a combat mission, never justified its cost, never became what its designers intended. That reading misses the point. The XB-70 answered questions that no one had tools to answer before it flew - questions about inlet shockwave management, thermal structural design, compression lift behavior, and large-aircraft aerodynamics at the edge of the atmosphere. That knowledge did not disappear when McNamara canceled the production line.

The engineers who conceived this aircraft in Inglewood, California in 1958 believed it was achievable. They were right.

Key Takeaways

The XB-70 Valkyrie was designed to cruise at Mach 3 at 70,000 feet, using compression lift from its own shockwave as a core efficiency mechanism - with hinged wingtips folding down 65 degrees to enhance the effect at speed
The production program was canceled in 1961 by Secretary McNamara - not because the aircraft failed technically, but because ICBMs made the manned high-speed bomber concept strategically obsolete
AV-2 was lost in a midair collision on June 8, 1966, killing NASA pilot Joe Walker and co-pilot Major Carl Cross during a formation flight arranged for a publicity photograph
The flight research data generated by the program directly influenced supersonic transport development in the United States and contributed to the engineering foundation behind the Concorde
AV-1 survives at the National Museum of the United States Air Force in Dayton, Ohio - free admission, open to the public, and unlike anything else in any building anywhere