Not so long ago, anyone with the (considerable) means and the inclination could take a flight across the Atlantic at two times the speed of sound in the world’s first supersonic airliner, the Concorde.
At takeoff, the Concorde’s afterburners roared, rattling the fuselage, filling the cabin with the faint smell of jet fuel, and pressing passengers into their seat backs. But by the time the aircraft reached full speed over the open ocean, there was little to indicate they’d broken the sound barrier beyond a digital speedometer and the start of champagne service.
While passengers enjoyed bubbly, caviar, and proximity to celebrities, the sleek, luxury aircraft would scream across the sky higher and faster than any other jetliner, delivering its passengers to their destination in half the usual time.
It took two nations 15 years and $2.8 billion (more than 20 times the initial estimate) to get the Concorde off the ground. British Airways and Air France began shuttling passengers around in 1976, but the aircraft flew limited routes: the Concorde could only reach top speeds over the ocean, where the sonic boom that trailed the planes couldn’t terrorize people on the ground. That and the $12,000 ticket price ensured that the Concorde rarely flew more than half full, while burning several times more jet fuel and creating three times more noise, carbon, and nitrogen pollution.
The Concorde made its final flight in 2003. But now a new era of supersonic commercial flights is about to take off.
Boom Supersonic promises to put passengers in what the startup’s founder and CEO Blake Scholl has called the “son of the Concorde” by the end of the decade. And the Denver-based company plans to break ground on its manufacturing “Superfactory” at Greensboro’s Piedmont Triad International Airport in a matter of months, where it will make its flagship jetliner, the Overture. More than a century after the Wright Brothers made North Carolina first in aviation, Boom is poised to make it the fastest.
But aviation experts are questioning whether the Overture will—or should—ever take off.
Higher, Farther, Faster
It’s not just North Carolina’s storied aviation history that attracted Boom to the eastern seaboard. With its headquarters landlocked in Colorado, Boom needed to build its manufacturing facility closer to the Atlantic, where supersonic flight testing can take place.
Boom could have chosen from a handful of locations, but more than $121 million in combined city, county, and state incentives helped North Carolina outcompete contenders like Florida and Georgia.
It’s part of the state’s bigger play to attract businesses. Since 2021, North Carolina has attracted at least $17 billion in investments from companies like Apple, Toyota, and electric-car maker VinFast, which won a record-breaking $1.2 billion incentives package from the state in July.
The state also has one of the fastest-growing aerospace sectors in the nation, a military population that largely specializes in propulsion, a top-notch university system that would serve as a pipeline for an educated workforce, and roughly 1,000 acres of land at the Piedmont Triad International Airport set aside for exactly the kind of manufacturing facility Boom needs.
“We have been preparing this airport for projects like these and companies like this for the better part of 10 years,” said Kevin Baker, executive director of the Piedmont Triad Airport Authority.
Boom will occupy 65 acres at the airport, joining a cluster of aerospace companies in the region, including Honda Aircraft Company, Textron Aviation, and FedEx Express. The North Carolina legislature set aside $107 million for the expansion of roads and utilities to the company’s airport parcel and for the construction of the factory itself, which should begin in the next few months, according to Baker.
In return, Boom is expected to add more than 1,700 jobs and $500 million to the state’s economy over the next decade. For each job created, the state will reimburse Boom via a job-development investment grant, ensuring that the company invests in jobs over automation.
“It is both poetic and logical that Boom Supersonic would choose the state that’s first in flight for its first manufacturing plant,” Gov. Roy Cooper said in a statement announcing the deal. “Like the success of the Wright Brothers at Kitty Hawk, this innovative company will succeed by transforming passenger air travel with speed and sustainable energy.”
And Boom promises radical transformation: The company’s founder, Blake Scholl, has said repeatedly that its goal is delivering passengers “anywhere in the world in four hours for $100.”
Scholl, who grew up in Cincinnati, an hour south of the Wright Brothers’ hometown of Dayton, is an amateur pilot and a software engineer. After selling an e-commerce apps platform he developed to Groupon, Scholl told The Guardian he “wanted to work on the most important thing [for society] that’s not impossible.”
The one that would bring him the most joy, he decided, was the return of supersonic flight.
Scholl funneled half his life savings into the early research, hiring half a dozen aerospace engineers out of his own pocket before he began raising capital from outside investors. He officially launched Boom Supersonic in 2014.
In 2016, Boom announced the design of the XB1, a prototype that will serve as a proof of concept for the design and materials planned for the Overture. Boom told Fast Company that year that the “baby boom” would make its first test flights by 2017. But five years later, it’s still in the pre-flight testing stage.
Overture, which will carry between 65 and 80 passengers at 60,000 feet and reach speeds of Mach 1.7, is slated to go into production by 2024. Boom expects test flights to begin in that year, and for Overture to carry its first passengers by 2029.
They predict tickets will cost around $5,000 per passenger, at least at first. Scholl says he aims to get ticket prices down to $100 by the second or third generation.
The airliner, Scholl said in a statement in July, will “fundamentally change how we think about distance.”
‘Famously Loud and Famously Dirty’
Commercial supersonic flight seemed an inevitability when U.S. Air Force Captain Chuck Yeager broke the sound barrier in an orange rocket plane over a dry lakebed in southern California in 1947.
“With aviation, the mantra has always been higher, farther, faster,” said Janet Bednarek, a professor of history at the University of Dayton. “By the late 1950s, aeroengineers in the U.S. and Great Britain were beginning to think very seriously about how to apply what they’d learned about supersonic flight to commercial aviation, so that not just the military could go higher, farther, faster, but the rest of us could as well.”
Of course, most of us never did.
To understand the challenges Boom faces now, it’s helpful to understand what grounded supersonic travel in the first place.
The death knell for the Concorde was heard long before the Concorde took off, in the form of a sonic boom.
All planes generate sound waves as they travel through the air, which billow out in every direction. Jetliners that travel faster than the speed of sound—about 770 miles per hour—catch up to the waves moving ahead of the aircraft. These sound waves build up on the frame, and then reach the ground all at once in a thundering wake that sweeps along the ground behind the plane.
As military and commercial supersonic flights took off, people on the ground complained about noise, broken windows, and even increased heart attacks. “People just did not want to have regular sonic booms in their backyards,” said Bednarek.
Governments around the globe quickly banned supersonic flights over land, which meant the Concorde could only fly at Mach 2 over the ocean—drastically limiting its flight paths and the market for supersonic travel.
“Air France and British Air never made money flying the Concorde, even with the outrageously high fares that people paid,” said Bednarek. “They flew it for national prestige.”
NASA has since developed a “low boom” aircraft, tweaking the design of the frame to prevent the sound waves from building up, which means they hit the ground as subtle thumps rather than a boom. It’s working with Lockheed Martin on this experimental plane, known as the X-59; test flights began this year. Depending on how communities react, the restrictions on overland flight for certain supersonic designs could eventually be lifted.
Boom claims that there are still hundreds of “supersonically viable routes airlines can profitably fly” over the open ocean. The company claims its jet will also fly roughly 20 percent faster than other subsonic jets overland, which have actually slowed down since the heyday of the Concorde. (Most modern airlines sacrifice speed to increase fuel efficiency and meet more stringent environmental regulations.)
“Concorde engines were famously loud and famously dirty,” said Dan Rutherford, director of the aviation and marine programs for the International Council on Clean Transportation, a nonprofit that provides independent analyses of environmental policies. “They had these afterburners that they used to create enough thrust to achieve supersonic flight. You could never build that aircraft today, because of environmental regulations.”
Boom’s most recent Overture redesign also incorporated new noise-reducing features, a company spokesperson said via email, “ensuring that supersonic takeoff is no louder than today’s largest subsonic jets for airports and surrounding communities.”
But noise is only one kind of pollution. Aviation accounts for roughly 2.5 percent of global emissions—a share that is expected to grow as other industries decarbonize and demand for travel grows. Carbon emissions from aviation could triple by 2050, according to the United Nations; the ICCT expects they will grow even faster than that.
Boom’s plan to reduce the Overture’s emissions relies on the use of sustainable aviation fuels, or SAFs. Like standard jet fuel, these fuels are still carbon-based, but they’re made with biofuels or carbon pulled from the atmosphere through direct air-capture technologies. Most airlines today are incorporating sustainable fuel blends into their fleets, but SAFs make up less than 1 percent of what’s burned.
That’s at least partly because jet fuel provides a number of services to aircrafts beyond just powering flight, said Joshua Heyne, an associate professor at Washington State University. It helps balance the aircraft, pulls heat from the engine, and facilitates the expansion of O-rings that seal critical joints in the plumbing of aircraft. Aviation is a safety-conscious industry, and manufacturers and airlines need to be sure that alternative fuels can fulfill the same functions.
Boom is confident that it will solve all of these engineering problems, and that Overture will be the first airliner “capable of using 100% SAF without blends or additives,” said a spokesperson via email.
Henri Werij, the dean of the faculty of aerospace engineering at Delft University of Technology in the Netherlands, is skeptical. Every major airline is interested in scaling up sustainable fuels and pushing for engine manufacturers to find solutions to these technical challenges. “The big manufacturers will have engines that run on 100 percent SAF sooner than there will be a Boom aircraft,” Werij said.
And just because a plane can run on 100 percent sustainable fuels, doesn’t mean it will. It’s the airline, not the manufacturer, that buys the fuel—and right now, there just isn’t enough SAF to go around. “Basically, if you ran all of the world’s fleet on 100 percent SAFs, it would run out of fuel in four hours,” said Rutherford.
In September, Boom announced an agreement with Air Company, a carbon utilization startup that uses captured carbon to make various products, including vodka and, now, fuel. Boom has signed on to purchase up to 5 million gallons annually for Overture test flights.
By the time supersonics are operational, airlines could be spending 25 times more to fuel a supersonic jet with sustainable fuels than a subsonic jet with conventional fuel.
“The economics of supersonics has never been good,” said Rutherford. “If you impose either an overland flight ban or require the use of SAFs, the market basically completely disappears.”
Carbon emissions are only one facet of sustainability. Werij notes that the latest science shows aviation’s climate impact is two to three times higher than the carbon dioxide emissions alone; the clouds that form around engine exhaust and other pollutants released when jet fuel is burned also contribute to ozone depletion and warming.
The impacts of non–carbon dioxide pollutants, which remain in the atmosphere for anywhere from minutes to months, are not as well understood, said Bill Hemmings, the former director of shipping and aviation for the sustainability NGO Transport and Environment. But that doesn’t mean that they aren’t significant.
“They are so powerful that, combined, they heat the planet far more every day than all the aviation CO2 that has so far accumulated in the atmosphere since the Wright Brothers first took off,” Hemmings wrote in 2019.
Boom says that flying on 100 percent SAFs can also reduce emissions of sulfur oxides and particulate matter. And while experts have long said that the higher cruising altitude of supersonics contributes to its larger environmental footprint because those pollutants tend to hang around in the atmosphere for longer, Boom claims that it also comes with benefits. Flying at a higher altitude, for example, may lead to fewer contrails, which account for a large chunk of aviation’s climate footprint.
While route, temperature, speed, and humidity all play a role in just how much is emitted, as a 2022 review in the journal Aerospace noted, the net impact is not fully understood.
“The non–carbon dioxide climate impact of supersonics could be anywhere from 20 to more than 200 times that of subsonics,” said Rutherford. “There’s a suite of potential problems with the technology that are quite concerning.”
A Supersonic Glider
The average traveler may not have broken the sound barrier since 2003, but that doesn’t mean the aviation industry hasn’t made significant advancements since the Concorde was designed and built.
Kathy Savitt, Boom’s chief business officer, has said that the company is capitalizing on more than 50 years of advancements in propulsion, materials, and modeling. Where the Concorde design was tested in expensive wind tunnels, Overture has been fine-tuned using complex computer models; where the Concorde was aluminum, Overture will be made from carbon composites; and where the Concorde was powered by notoriously noisy and polluting turbo jets, Overture will be powered by—well, that remains to be seen.
Overture’s engine will be unlike anything that’s been built before: a medium-bypass turbofan engine, without the infamous afterburners and capable of running on 100 percent SAFs. The trouble is, designing an engine from scratch is incredibly expensive, and one important question remains unanswered: Who will build it?
The London-based engine manufacturer Rolls-Royce, which also worked on the Concorde engine, contracted with Boom in 2020 to conduct engineering studies on potential engine designs. But Rolls-Royce announced in September that its contract with Boom had ended.
Several other engine suppliers—including Honeywell, Safran Aircraft Engines, and General Electric, which had previously partnered with an erstwhile supersonic rival, Aerion—told the aviation site Flight Global that they have “no interest in developing engines for civil supersonic aircraft.” Until Aerion ceased operations in May 2021, citing a lack of funds, many considered it to have the best shot at bringing back supersonic passenger travel.
In October, Gaël Méheust, the president and CEO of engine supplier CFM, demurred as well. “We don’t see a significant market for an engine that targets a very small potential niche,” he said at a conference.
Boom may have to fund the engine design itself—which is part of what bankrupted Aerion.
“It’s a supersonic glider at this point,” said Rutherford.
In total, Boom estimates that it will take between $6 billion and $8 billion to bring Overture to market—funding that the company says will come from equity fundraising, airline prepayments, supplier commitments, and other sources. The company has announced some $270 million in funding so far, which includes investments from interested airlines and the military.
United Airlines was the first U.S. airline to sign up to buy 15 of Boom’s Overture aircrafts in summer 2021; a year later, American Airlines announced a deal to purchase up to 20. In January 2022, Boom announced a $60 million contract from the U.S. Air Force that will go toward Overture research and development.
In the meantime, construction work continues at the Piedmont International Airport. “Until such time that we hear different, we’re moving ahead,” said Baker.
Boom still appears to be moving forward. In September, the company announced that it would work with Advanced Integration Technology to provide the custom equipment and automation tooling for Overture’s assembly. In early October, the state Department of Transportation closed down the shoulders along a three-mile stretch of Interstate 73 to begin work on access roads and an overpass for Boom.
Scholl said that the company will announce its new engine partner by the end of the year. But experts say it’s unlikely the company can meet its 2026 test-flight deadline without an engine currently under development. “The claim that Overture is going to fly for the first time in 2026, and that they’re going to do it without an engine under development, is pretty wild,” said Rutherford.
“Boom Supersonic is a major and welcome addition to North Carolina’s aerospace industry cluster, and we have no concerns regarding their progress,” David Rhoades, the communications director for the North Carolina Department of Commerce, told The Assembly. Rhoades noted that the Job Development Investment Grant that the state awarded Boom doesn’t kick in until 2026.
As a hedge on the state’s investment, anything built for Boom could potentially be used by other interested manufacturers, Baker noted. “And we have lots of interest,” he said. “Right now, we’re worried that the thousand acres isn’t going to be enough, frankly.”
A Different World
Whether or not Boom can build its own engine is less pressing than whether it should.
If and when Boom takes off, it will be flying in a completely different world than the Concorde, one ravaged by climate change and the inescapable knowledge of our role in it. Boom is facing a social and political climate that is increasingly hostile to frivolous aviation.
A “flying shame” movement is currently thriving in Europe, which encourages travelers to opt for more sustainable forms of transport like railways. In the U.S., celebrities have come under fire for taking absurdly short flights on private jets. Governments are beginning to take action, too: This year, Israel announced that it will close its airports to Boeing 747s and other four-engine planes starting in 2023, in order to reduce noise and air pollution within its borders.
Given all these challenges, why revive supersonics at all?
“The headwinds for this are huge,” Rutherford said. “There’s never been a private company that’s built a supersonic plane before, then you’ve got climate change, COVID, a retrenchment of business travel, flying shame. I’m amazed at how unlucky the company is, to be honest. But Blake has a vision, and he’s been pushing forward with it.”
The aviation industry is no stranger to skepticism. Even as the Wright Brothers were taking to the skies above Kitty Hawk in their homemade gliders, experts were confidently stating that flying machines would remain in the realm of dreams. George Melville, the chief engineer of the U.S. Navy, wrote in 1901, “A calm survey of certain natural phenomena leads the engineer to pronounce all confident prophecies for future success as wholly unwarranted, if not absurd.”
Two years later, the brothers took off in the first engine-powered aircraft.
Supersonic skeptics and supporters do agree that the industry is on the brink of a new era. In just the first two decades of the 20th century, aviation saw a revolution, from the Wright brothers’ gliders to the first transoceanic flight.
“We are at a point in time where a new revolution should happen. The changes we have to make are enormous,” Werij said. “I don’t think that that revolution means that we have to go faster.”
Bednarek, the University of Dayton historian, agrees that there are more important concerns.
“The technological challenge that we ought to be focusing on is decarbonizing aviation,” she said. “Making [aircraft] more efficient, finding alternative fuels, finding alternative propulsion systems—in an era of climate change, those would probably have a bigger, broader social impact, a more important social impact, than a supersonic airliner.”
Kate Wheeling is a freelance journalist based in Santa Barbara, California, with a focus on environmental justice and climate change. You can find her work in Smithsonian Magazine, The Daily Beast, Mother Jones, and other publications.