Key point: While the B-29 was responsible for the three deadliest bombing raids in history—the firebombing of Tokyo and the nuclear bombings of Hiroshima and Nagasaki—its successor the B-50 never dropped a bomb in anger.

Quiz time! Which secret American military project during World War II proved even more expensive than the $2 billion Manhattan Project which developed U.S. atomic bombs?

That would be the $3 billion B-29 Superfortress—the huge four-engine bomber designed to fly across huge distances and drop those atomic bombs.

The silver-skinned B-29’s four huge turbo-supercharged R-3350 Duplex Cyclone radial engines allowed the 37-ton aircraft (when empty!) to fly relatively fast at 290 to 350 miles per hour and at altitudes exceeding 30,000 feet, making it extremely difficult for Japanese interceptors to catch up with them.

But even as World War II ground on to its conclusion, the Air Force appreciated that the Superfortress’s advantages would soon vanish due to the advent of turbojet-powered fighters. As the Cold War gathered momentum in the late 1940s, it further became vital for the Air Force to have a nuclear bomber that could strike Russia from U.S. bases.

These needs culminated in a new B-29D model with engine power cranked up nearly 60 percent using a 3,500 horsepower R-4360 Wasp Major engine and a skin made of stronger but lighter 75-S aluminum alloy. Together, this lowered the weight of the wings by 600 pounds and increased speed to nearly 400 miles per hour. Other trimmings included a taller tail fin, hydraulically assisted controls, and wing and window de-icing systems.

The end of World War II saw the cancellation of B-29 orders. To rescue the program, the military redesignated the B-29D as the B-50 to imply the aircraft incorporated more original design features than was actually the case—hardly the first nor the last time misleading aircraft designations have been adopted for political purposes.

Only a small run of sixty B-50As were produced in Washington, and these went onto become the tip of the newly-formed Strategic Air Command’s nuclear deterrence fleet in 1948 until huge B-36 Peacemaker and B-47 Stratojet jet bombers could enter service.

A small number of B-50Bs were then built with lighter-weight fuel cells, until the Air Force settled on the B-50D to commit to larger-scale manufacture of 222 bombers. The last model downsized the crew from eleven to eight, had provisions for external fuel tanks, featured a simplified nose cone, and included a built-in inflight-refueling boom.

The B-50 fleet suffered its share of teething issues too due to defective pressure regulators, engine problems, and cracking of its aluminum skin which took several years to iron out. Furthermore, as the Pentagon kept on rapidly deploying new types of nuclear bombs, the B-50 bombers had to be repeatedly converted to fit them in their bomb bays.

When the Korean War broke out in the 1950s, only the older B-29s were called into perform non-nuclear strikes—where they suffered unexpected losses to Soviet MiG-15 jet fighters. With speeds approaching 680 miles per hour and high climb rates, the MiG-15 demonstrated that even the B-50’s higher speeds and altitudes were of little advantage due to advancing jet technology. This led to the cancellation in 1949 of an experimentally re-engined model first called the YB-50C with 4,500-horsepower engines.

However, the B-29 and B-50 by then were at the forefront of pioneering air-to-air refueling technology, which would allow the kind of extended range bombing raids the SAC was aiming for. Initially, this involved converting B-29s into KB-29s tankers, that would use a long hose to refuel nuclear-armed B-50s.

In 1949, the B-50A Lucky Lady II became the first aircraft to fly around the world in an epic ninety-four-hour flight between February 26 and March 2. (An earlier attempt by B-50 Global Queen, had to be aborted due to engine failures.) She was refueled by no less than four pairs of KB-29M tankers flying out of the Azores, Saudi Arabia, the Philippines and Hawaii along its 23,452 mile-long journey. This record would finally be beaten in 1956 in less than half the time by a brand-new B-52 jet bomber.

Before that, in 1953 jet-powered B-47s began entering service while B-29s came to be retired, so it naturally fell to B-50s to take on the support duties. Ironically, the B-50 would go on to see far more action in these support roles than as a bomber.

Altogether 136 B-50s were converted into KB-50 tankers. Starting in 1956, 112 were further modified into the KB-50J model by adding J-47 turbojet engines from the B-47 bomber to help them sustain higher speeds and altitudes to keep up with the bombers they were refueling. The add-on turbojets boosted the KB-50J’s maximum speed to 444 miles per hour—slightly faster than a World War II-era Mustang fighter.

The RB-50B and RB-50E were photo-reconnaissance planes dispatched on increasingly dangerous overflights over Soviet and North Korean airspace. Some of these “ferret” missions were even intended to provoke Soviet intercepts, allowing U.S. spies to listen in on the resulting radio chatter and radar activity, studying what kind of defenses were in place.

The RB-50G was an electronic spy plane full of special consuls, with an expanded crew of sixteen. This too proved a risky mission: in 1953 the RB-50G Little Red Ass was shot down over the near Vladivostok by two MiG-17 fighters. Of aircraft’s eighteen crew that managed to bail out, only the co-pilot survived the freezing waters of the Sea of Japan to be rescued by a U.S. destroyer.

There was even the WB-50D, a “hurricane hunter” plane operated by the National Weather Service to track violent weather events—and also sample radiation levels in the to monitor Soviet nuclear tests during the early 1950s. These saw so much rough duty that six WB-50s were lost with the total loss of their crew. Weather reconnaissance reports from WB-50s were instrumental in planning the U-2 spy plane flights that discovered Soviet nuclear missiles in Cuba, triggering the Cuban Missile Crisis.

The various B-50 variants were finally retired in the 1950s, their aluminum airframe aging poorly after seeing much hard use. A half-century later, the C-135 family of planes based on the 707 airliner continue to perform the numerous support roles the B-50 had pioneered—especially the air-to-air refueling technology which continues to undergird U.S. airpower into the twenty-first century.

While the B-29 was responsible for the three deadliest bombing raids in history—the firebombing of Tokyo and the nuclear bombings of Hiroshima and Nagasaki—its successor the B-50 never dropped a bomb in anger.

However, it would not be entirely accurate to say it never fired a shot in combat. The RB-53G that was shot down near Vladivostok fired back ineffectively at its pursuers. And in March 15, 1953 a WB-50 flying in international airspace near the Kamchatka peninsula was intercepted by two MiG-15 fighters. These tailed weather-recon plane for a while before one opened fire, and the WB-50’s tail gunner shot back. Fortunately, this time everyone returned to base.

Sébastien Roblin holds a master’s degree in conflict resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring. This article first appeared last month.

Image: Wikipedia.