The 10 Most Compelling Aircraft That Didn’t Succeed

Since prehistoric times, humans have always made comparisons. Ancient humans noticed that some people were taller than others. They also noticed that each person had strengths others didn’t possess and weaknesses or areas for improvement. These two features—strength and weakness—have defined human ambitions for millennia.

In 1903, the Wright brothers achieved the first powered flight in a heavier-than-air machine at Kitty Hawk, North Carolina. Their aircraft reached a ground speed of 6.8 miles per hour during its 12-second flight, covering 120 feet (36.5 meters). This achievement sparked and ignited the imaginations of all of humanity. Immediately, the race began to surpass the Wright brothers’ breakthrough, and that race has not slowed down or stopped in the last 120 years.

In this list, we’ll start soaring in the stratosphere, cruising at altitudes between 6 and 31 miles (10 and 50 km) above the Earth’s surface. Then, we’ll take a steep nosedive to explore ten unbelievable aircraft ideas that, for a variety of reasons, never managed to complete their flight readiness checklists.

These are ten remarkable projects that couldn’t overcome the weighty problems that kept them grounded. But don’t be discouraged by these unrealized visions. Humanity always learns from its failings and mistakes in the long run. We should look at this list as ten opportunities for us to learn just how difficult it is to get advanced aircraft projects in the air. This is your captain: please sit back, relax, and get ready for takeoff.

Related: Top 10 Terrifying Facts About Airplanes

10 America’s First Jet Bomber Missed the Target

The Douglas XB-43 Jetmaster was America’s first jet bomber, but most of the general populace has never heard of it. Born out of World War II urgency, it was designed to replace the piston engines of the XB-42 Mixmaster with cutting-edge General Electric J35 turbojets. The new design made an unequivocal promise: greater speed and a sleek, modern profile. When it first took to the skies in 1946, it showed real potential, hitting speeds of 515 mph (320 km/h) while carrying up to 8,000 pounds (3,629 kg)of bombs. For a brief moment, it seemed like the future of military aviation.

But the timing wasn’t on the Jetmaster’s side: World War II had ended, and the United States’ military priorities shifted. Jet engines were still in their infancy, and delays in production meant that the XB-43 was outdated before it ever flew. By the time its prototypes were tested, newer, better designs, like the North American B-45 Tornado, were already in development.

Still, the XB-43 paved the way for the jet-powered bombers that followed. It was a bold step into the jet age, but it failed to keep pace with its newer competitors.^[1]

9 The Rockwell XFV-12

In the early 1970s, the U.S. Navy envisioned a supersonic Vertical Takeoff and Landing (VTOL) fighter for its proposed Sea Control Ships (SCS). Rockwell’s XFV-12 promised to deliver this capability with its novel Thrust Augmenter Wing (TAW) system, which redirected engine exhaust through vents in its wings and canards to achieve lift. By integrating components from the A-4 Skyhawk and F-4 Phantom, Rockwell aimed to significantly reduce the cost of production of the XFV-12.

Theoretically, the XFV-12 would outperform rivals like the Harrier, reaching Mach 2 speeds with its powerful Pratt & Whitney F401 engine. Its air-to-air weaponry, two AIM-7 Sparrows and two AIM-9 Sidewinders, also surpassed the Harrier’s capabilities at the time. However, the TAW system proved to be the aircraft’s downfall. During testing, it failed to generate enough lift, producing only a fraction of the expected thrust.

By 1978, cost overruns and fundamental design flaws doomed the XFV-12 to an early grave before it ever took flight. Despite its potential, the XFV-12 project remains a compelling example of an ambitious state-of-the-art military aircraft vision that was grounded by the unwavering realities of physics and advanced engineering.^[2]

8 The Dornier Do 31

The Dornier Do 31 was an experimental aircraft born during a 1960s period when West Germany and other European nations felt threatened by the Cold War with the Soviet Union. Facing potential Soviet attacks on airfields, West Germany sought a jet-powered Vertical Takeoff and Landing (VTOL) transport capable of operating from highways and short airstrips. Dornier, a company renowned for its flying boats and airliners, rose to the challenge, designing the Do 31 as the world’s only Vertical Takeoff and Landing jet transport aircraft.

The Do 31 featured two powerful Rolls-Royce Pegasus turbofan engines under its wings and eight additional turbojets housed in wingtip nacelles for vertical thrust. This ten-engine configuration produced a staggering 66,200 pounds of thrust. The aircraft’s hybrid analog-digital flight computer ensured stability, a critical necessity given the complexity of transitioning between vertical and horizontal flight. Despite its innovative design, the sheer engineering hurdles proved overwhelming.

By 1970, spiraling costs and limited military interest grounded the Do 31. Though never mass-produced, it remains a testament to daring aerospace ingenuity and an enduring icon of Vertical Takeoff and Landing experimentation. An interesting fact is that aviation enthusiasts can experience the Dornier Do 31 firsthand by flying it in Microsoft Flight Simulator.^[3]

7 The XF-84H Thunderscreech

The Republic XF-84H, better known as “Thunderscreech,” was an experiment in noise, speed, and pure chaos. This experimental aircraft was designed to be the fastest propeller-driven plane of its time. Instead, it became infamous for its ear-splitting noise. Its propeller tips spun so fast that they broke the sound barrier, creating a screech so loud that it could be heard 25 miles (10.2 km) away. On the ground, the noise was unbearable. It caused nausea, migraines, and even seizures for anyone unlucky enough to be nearby.

The XF-84H wasn’t just loud; it was a mechanical nightmare. It combined a turbojet engine with a massive propeller, an idea that seemed clever at the time but that proved to be completely unworkable. The vibrations shook the plane to its core, and its unpredictable handling terrified pilots. Ground crews hated it, pilots dreaded it, and aviation experts soon realized that it was simply too flawed to ever succeed. It completed only 12 test flights before being officially scrapped.

While the Thunderscreech never saw action, it left a lasting legacy of engineers trying to push the boundaries of design. It taught a very important lesson: sometimes projects fail; it’s a natural part of the continuous improvement process. One just has to learn from the failures and use what they’ve learned to improve their future designs.^[4]

6 The Boeing X-32

In the late 1990s, Boeing’s X-32A was a heavyweight contender for the ambitious Joint Strike Fighter (JSF) program. This program aimed to create a versatile fighter jet that could meet the needs of the U.S. Air Force, Navy, and Marine Corps. The X-32A was designed for conventional take-offs and landings, short take-offs and vertical landings, and even carrier operations. Its odd delta-wing design and oversized air intake made it stand out, but not always in a good way.

The X-32A took to the skies in September 2000 for its first flight. Over the next four months, it completed 66 test flights, showcasing its capabilities in areas like in-flight refueling, weapons handling, and supersonic speeds. While the aircraft proved to be functional, it had many significant drawbacks. Its design was seen as less practical and less aesthetically appealing than its closest rival, the Lockheed Martin X-35. In the end, the X-35 won the contract, and it went on to become the F-35 Lightning II.

The X-32 never saw active duty, but it wasn’t completely forgotten. After the competition, the prototype was retired and later moved to the National Museum of the United States Air Force. Today, it has caught the attention of a new generation of future aviators and aviation historians, thanks to its unique look, story, and aircraft design principles.^[5]

5 The B-58 Hustler

The B-58 Hustler is probably the most successful plane on this list: I debated for a long time whether to include it at all. Ultimately, I decided that it belonged: let me tell you why. This supersonic nuclear bomber actually entered service, unlike most of the other aircraft on this list. However, it was only in service for a decade (from 1960 to 1970). Its short career stemmed from three major flaws: (1) exorbitantly high operating costs, (2) incredibly complex maintenance requirements, and (3) a fatal vulnerability to surface-to-air missiles. These weaknesses ultimately led to the plane’s early retirement.

The Convair B-58 Hustler was undeniably fast, and it was a revolutionary milestone in supersonic aviation. Introduced in the late 1950s, it became the U.S. Air Force’s first bomber capable of sustained Mach 2 flight. Its sleek, delta-wing design looked futuristic, and its deafening roar during supersonic runs grabbed everyone’s attention. Designed to deliver nuclear weapons at supersonic speeds, the Hustler was a vital Cold War asset. However, its promise was overshadowed by its limitations and weaknesses. [6]

San Antonio’s Kelly Air Force Base played a central role in the B-58’s story. Starting in 1955, the base managed everything from routine maintenance to extensive modifications. By the 1960s, Kelly launched the ambitious “Hustle-Up” program, upgrading the fleet with enhanced ejection systems and multi-weapon payload capabilities. Despite these efforts, the Hustler’s days were numbered. One plane, nicknamed “Firefly II,” ended its flying days after sustaining damage in 1968. Lovingly restored by the Kelly team, it was placed on display at Kelly Air Force Base in 1991.^[6]

4 The YF-12

The Lockheed YF-12 was a plane of epic potential that never achieved the destiny envisioned by its creators. Designed in the late 1950s by the legendary Skunk Works team, it was a fighter-interceptor version of the A-12 reconnaissance plane. This sleek, black aircraft was built to break all existing speed records, and it did. On May 1, 1965, the YF-12 reached an incredible 2,070 mph (3,331 km/h) and soared to 80,257 feet (24,462 m), setting speed and altitude records that stunned the entire advanced aviation community. Yet, despite its jaw-dropping performance, like most of the aircraft on this list, it never made it to operational status. Instead, it was quietly shelved, overshadowed by its much more successful cousin, the SR-71 Blackbird.

NASA and the U.S. Air Force saw potential in the YF-12, and they decided to give it a second life. Starting in 1969, two aircraft were used for experimental research on Mach 3 flight. The program pushed the limits of what was possible, studying the effects of extreme heat and pressure on an aircraft at such speeds. But the journey wasn’t without setbacks. One YF-12 was lost to an in-flight fire in 1971, and the program’s long-term ambitions began to fade.

By the late 1970s, the YF-12’s days were done for good. NASA had shifted its focus to efficiency over speed, and the program was retired after 297 flights. The surviving YF-12 is proudly displayed at the National Museum of the U.S. Air Force in Dayton, Ohio, located at Wright-Patterson Air Force Base.^[7]

3 The Grounded British Wonder Plane

The British Aircraft Corporation TSR-2 was originally destined to revolutionize tactical strike and reconnaissance missions, but things didn’t unfold as planned. Designed and conceived in the early 1960s, the aircraft boasted cutting-edge technology like terrain-following radar and the ability to cruise at supersonic speeds while flying low. It wasn’t just sleek; it was also versatile, capable of launching nuclear or conventional weapons and operating from rough airstrips. The TSR-2 was supposed to be a bold progression into the future of aviation.

However, the ambitious TSR-2 project came with an unexpectedly exorbitant price. Development costs rose exponentially, technical hurdles piled up, and the political winds in the United Kingdom shifted. The first prototype, XR219, took flight in 1964 and performed brilliantly, exceeding all expectations. But when things seemed to be taking off, an unforeseen calamity struck. In 1965, the British government abruptly pulled the plug on the program, citing its uncontrollably ballooning budget. Instead, they opted to purchase the American F-111. Most TSR-2 prototypes were destroyed, and the tactical and reconnaissance aviation dream that was the TSR-2 was grounded forever.

The TSR-2’s cancellation represents one of aviation history’s greatest “what-ifs.” Today, a few surviving airframes, like the XR220, are on display in museums. However, history always has the power to bring good ideas that failed in the past to fruition at some point in the future. Future aviation projects might steal some of the good ideas that were incorporated into the TSR-2.^[8]

2 Canada’s Broken Supersonic Arrow

In the 1950s, Canada had grand ambitions for its new Avro Arrow project, a sleek interceptor designed to protect its skies from potential Soviet threats. It was a bold vision: a delta-wing jet that could hit Mach 2 speeds (1,534 mph or 2,468 km/h) and soar above 50,000 feet (15,240 m). With advanced engines and state-of-the-art avionics, the Arrow was an exciting aircraft and a powerful declaration of Canada’s aerospace capabilities.

The Arrow’s first flight took place in 1958, and it was a triumphant achievement. The plane performed brilliantly, showcasing its potential to redefine Canada’s air defenses. But, as we’ve learned from other ambitious aircraft projects on this list, big dreams usually come with equally inflated costs. The project’s expenses spiraled out of control, and Canada’s defense priorities suddenly shifted. In 1959, Prime Minister John Diefenbaker made a highly unexpected decision: he canceled the project. Worse, the government ordered all Avro Arrow prototypes and blueprints destroyed. The dream was wiped out, and thousands of jobs disappeared overnight.

As we’ve seen with many projects on this list, the Avro Arrow had enormous potential, but Canada simply couldn’t, or wouldn’t, afford the incredibly expensive project. Many see its cancellation as the blow that crippled Canada’s aerospace industry, while others defend it as a prudent, long-term financial decision. Given that the Cold War ended almost four decades ago and that Canada doesn’t seem to need such powerful defensive capabilities today, history may one day conclude that they made the right decision to cancel the Avro Arrow project.^[9]

1 The Ambitious XB-70 Valkyrie

In the late 1950s, the United States embarked on an ambitious project to develop the North American XB-70 Valkyrie, a strategic bomber capable of cruising at Mach 3 (2,301 mph or 3,705 km/h) and altitudes exceeding 70,000 feet (21,336 m). This impressive aircraft was designed to outrun and outmaneuver enemy defenses, delivering nuclear payloads deep into hostile territory. Its sleek, futuristic design and advanced engineering made it a symbol of American aerospace innovation during the Cold War.

Despite its groundbreaking design, the XB-70 program faced significant challenges. Advancements in surface-to-air missile technology and the shift toward intercontinental ballistic missiles (ICBMs) as primary nuclear delivery systems rendered high-speed manned bombers less essential and less practical. These strategic changes, coupled with escalating development costs, led to the program’s cancellation after producing only two prototypes. Tragically, one of these aircraft was lost in a mid-air collision during a test flight in 1966, resulting in the deaths of two crew members.

Though the XB-70 was never enlisted into active service, its design was decades ahead of its time, and it still looks surprisingly modern, almost 70 years after it was originally conceived.^[10]