Before the U-2 Spy Plane, There Was the X-16
The U.S. Air Force pushed hard for a larger aerial spy—before backing its competitor
In the early 1950s, the U.S. Air Force needed a new spy plane. While the flying branch ultimately backed development of Lockheed’s iconic U-2, the service initially pushed hard for another, larger design—the X-16.
In December 1953, Bell Aircraft Corporation submitted a proposal to Air Force officials for a high-altitude reconnaissance plane.
Five months earlier, the flying branch asked both Bell and Fairchild to come up with unique surveillance aircraft. Both companies worked hard to develop the planes — but neither were successful.
The Air Force recently released a redacted copy of Bell’s study through its Freedom of Information Act Website. We’ve pored through it—and found a revealing glimpse at the company’s failed attempt to build a Cold War spy plane.
At the time, high-altitude aerial spies were fairly theoretical—and on the edge of what was possible. But the tactics of aerial spying had changed.
When Bell submitted its report, the Pentagon had few options for snooping on the Soviet Union. In both World Wars and during the fighting in Korea, American aircraft had snapped photographs from the sky to help out troops on the ground.
But the Air Force hadn’t really considered the prospect of secretly spying on a foreign country from the air during peacetime.
Reconnaissance planes available during the era—mostly converted bombers—couldn’t outrun enemy fighters or avoid radars. And after seeing the outcome of Allied bombing campaigns over Germany and Japan, the Soviet Union had rapidly expanded its air defenses.
In 1950, Soviet fighters shot down a U.S. Navy Privateer patrol plane over the Baltic sea. Two years later, the Air Force lost a pair RB-29 intelligence aircraft over the Pacific in the space of five months.
“Aerial reconnaissance of the Soviet Union and surrounding areas had become a very dangerous business,” Gregory Pedlow and Donald Welzenbach wrote in the CIA’s official history of the U-2 program.
In 1952, a collection of academics known as the Beacon Hill Study Group gathered in Boston, Massachusetts to look into the Air Force’s intelligence gap.
“In the post-war world, intelligence and reconnaissance are more important to the United States by several orders of magnitude than ever before,” the final Beacon Hill report declared to Air Force officials. “They are crucial to some of the most fundamental aims in our national policy.”
The Beacon Hill team recommended the Air Force come up with a manned spy plane that could soar far above the Soviets’ defense network. The scientists also thought unmanned drones, rockets and balloons might work.
The resulting MX-2147 project demanded a plane that could fly a 3,000-mile round trip without refueling. The aircraft would have to get up to 65,000 feet and stay there for the bulk of the flight, according to Bell’s study.
At the required altitude, the Air Force believed that the aerial spy would be safe from the Kremlin’s newest fighter, the MiG-17. This first-generation fighter jet couldn’t get high enough to intercept the proposed American spy.
Bell’s proposed Models 103 and 105 looked very similar to Boeing’s contemporary B-47 bomber. Company drawings show a plane with swept-back wings, under-wing engine pods and a combination of large landing gear in the fuselage and small wheels on the wing tips.
A version of Pratt and Whitney’s then-new J-57 engine would power the new spy plane. These motors would later go on to serve a number of American military aircraft like the B-52 bomber, KC-135 tanker and Lockheed’s U-2.
We don’t know what sort of cameras Bell’s plane were supposed to carry. The Air Force redacted descriptions of the camera equipment and their schematics in the document—the only portions the flying branch redacted.
Almost a year after starting the MX-2147 program, the Air Force chose Bell’s offering over Fairchild’s proposal. The flying branch also asked the Martin Company to modify its B-57 bomber—a license-produced version of the English Electric Canberra—as a more immediate solution.
To hide the true nature of the program from Soviet spies, the Air Force referred to Bell’s aircraft as the X-16. This “X-plane” moniker is how the branch refers to experimental aircraft used for research—rather than actual missions.
But this was likely a means to conceal the nature of the program.
“The X-16 was the most blatant misuse of the X-vehicle designation system,” Dennis Jenkins, Tony Landis and Jay Miller wrote in the NASA monograph American X-Vehicles: An Inventory—X-1 to X-50. “It was simply an attempt to hide what would today be called a spy-plane.”
At the same time, Lockheed—Bell’s competitor—had learned of the MX-2147 project. So the company quickly began work on its own spy plane.
Famed Lockheed engineer Clarence “Kelly” Johnson came up with what amounted to a powered glider—called the CL-282. This design also had a number of features lifted from Johnson’s high-speed F-104 interceptor.
With their own airplane already in development, senior Air Force officials weren’t interested in Lockheed’s proposal. Gen. Curtis LeMay, chief of Strategic Air Command, was especially dismissive.
“General LeMay stood up halfway through the briefing, took his cigar out of his mouth, and told the briefers that, if he wanted high-altitude photographs, he would put cameras in his B-36 bombers,” Pedlow and Welzenbach wrote. “The general then left the room, remarking that the whole business was a waste of his time.”
Unfortunately, Bell ran into trouble as the company tried to actually build the X-16. To meet the Air Force’s requirements, the firm’s engineers had to use a pioneering but extremely lightweight—and subsequently fragile and unstable—fuselage and wing.
“The X-16 was a designer’s nightmare—the wing was an extremely long-span high-aspect ratio unit that was significantly lighter and more flexible than any in existence at the time,” Jenkins, Landis and Miller wrote.
But Bell absolutely had to use the low-weight design. The reason was because engineers needed to save weight for armor plating, a pressurized cockpit and two J-57 engines.
Still on the hook for 28 X-16s, the Air Force stood behind Bell’s product. In the meantime, Lockheed had rallied support at the Central Intelligence Agency for its smaller intelligence aircraft—what would eventually become the U-2.
Air Force officials actively argued against letting the CIA proceed with Lockheed’s plan. The flying branch insisted that Johnson’s smaller design wouldn’t work without the J-57 engine—which the X-16s needed.
But Lockheed’s aircraft were simple and easy to design, and the company promised they could quickly be ready for action. On top of this, Pres. Dwight Eisenhower offered his personal support to the CIA’s proposal.
Eventually, the Air Force and the CIA agreed to ditch the X-16 and work together on the U-2.
In November 1954, Secretary of the Air Force Harold Talbott and CIA Director Allen Dulles, along with Johnson and others, sat down to lunch to hash out the details.
The flying branch and the spooks would work together, but the money would flow through the agency’s “unvouchered channels,” according to Pedlow and Welzenbach.
The Air Force quietly canceled the X-16, and Martin only built 20 special high-altitude RB-57Ds. Washington passed some of these modified bombers to Taiwan, while the Air Force used others to test electronic countermeasures.
Despite making one full-sized mock up, Bell never actually completed any functional X-16 prototypes. But they almost did—the first plane was 80 percent complete when the Air Force told them to stop.
In 1956, CIA flew its first U-2 over Warsaw Pact territory, and it still flies today. The proposed X-16 turned into a dim memory.