Mach Cut-Off Evidence Opened a Path for Overland Supersonic Flight

Blake Scholl argues that the most consequential result of XB-1 was not merely that it exceeded Mach 1. The aircraft gave Boom a way to address a regulatory constraint that had made a domestic supersonic market difficult to imagine.

XB-1 crossed the sound barrier six times on each of two flights, Scholl says, without producing an audible sonic boom on the ground. The flights demonstrated Mach cut-offA condition in which a sonic boom refracts upward in the atmosphere rather than reaching the ground.: at sufficient altitude, with the appropriate speed and weather conditions, the shock wave turns upward rather than arriving at the surface.

That result changed the policy problem. Supersonic flight had long raised a question about what level of boom would be quiet enough to permit overland operation. A boom that does not reach the ground, Scholl argues, eliminates the threshold argument altogether. The illustration shown during the presentation depicts shock waves curving upward from an aircraft over the desert rather than reaching the surface.

Boom was invited to the West Wing roughly 24 hours after the demonstration, according to Scholl. An executive order followed 115 days after the flight; he characterizes it as making supersonic flight legal again in the United States. A White House page shown during the presentation identifies the order as “Leading the World in Supersonic Flight,” dated June 6, 2025.

He separately describes legislation intended to make that policy change permanent. According to Scholl, a bill was introduced in both the House and Senate after the executive order, passed the House unanimously, and later cleared the Senate Commerce Committee with another unanimous vote.

The practical lesson is not simply that regulated industries can be navigated. A company can sometimes change the regulatory environment by creating evidence that reframes the issue.

That approach depended on the type of industry. Scholl contrasts Boom with Uber, where Travis Kalanick, in his telling, deployed before seeking regulatory approval and used a base of customers to counter taxi-industry opposition. He characterizes much regulation as a tool that entrenched interests use to avoid competition, rather than solely as a response to public-safety concerns.

Aviation was different. Boom was building a safety-critical product and did not face a comparable entrenched adversary. The company needed the FAA as a collaborator.

From the beginning of XB-1, Boom told the FAA what it was building, invited regulators to inspect its work, and offered plans before they were finalized. The aim was to make the relationship “Boom plus FAA versus the problem,” rather than Boom versus FAA. When Boom declared the aircraft ready to fly, Scholl says, an approval process that might otherwise take months took 90 minutes. The company also received its permit to fly a civil supersonic aircraft supersonically before XB-1’s first flight.

Blake Scholl began with a larger frustration: in 1969, the United States landed people on the moon and Concorde first flew. More than half a century later, commercial supersonic flight is gone, and the country has become slower at building consequential physical systems.

He points to a Wall Street Journal report shown on screen: a new Patriot missile interceptor takes Lockheed more than two years to produce and depends on more than 400 companies. Scholl presents that supply-chain complexity as evidence of an industrial system that cannot move at the pace its strategic needs demand.

Aviation, in his view, makes the stagnation visible. The Boeing 707 brought in the Jet Age in 1957; Boeing’s 787 does not fly faster, and Scholl notes that its launch was itself more than two decades ago. The first jets changed more than travel time. The DC-6, shown at 315 mph, gave way to the 707 at 600 mph.

Those speed changes altered activity on the ground. Hawaii became a mainstream destination because travelers could get from the United States to Honolulu in seven, eight, or nine hours. Nike’s early business of importing Japanese running shoes followed Phil Knight’s trip to Japan. The Beatles’ late-1960s world tour, Scholl says, would not have been practical a decade earlier with slower airplanes.

The relevant implication for industrial founders is that speed changes what markets and relationships can exist. Boom’s route-time maps make the claim concrete:

For Scholl, these are not simply premium-travel improvements. A three-and-a-half-hour Atlantic crossing or a Sydney trip made comparable to today’s Honolulu trip could, he suggests, produce the equivalent of the new destinations, businesses, and cultural exchange that emerged with the Jet Age.

Scholl set himself a lifetime goal of breaking the sound barrier in his mid-twenties. At first, he expected a business-jet manufacturer to revive supersonic travel. But the post-Concorde ban on supersonic overland flight in the United States undermined the business case for an aircraft whose customers would need to fly substantial domestic routes. Established business-jet companies did not want to pursue a legal change while financing an aircraft that might not become legal to operate.

A commercial airliner appeared still less likely to emerge from an incumbent. Scholl says Boeing was not building fundamentally new aircraft, much less a supersonic one. He recalls pitching Boom’s seed round to Jeff Bezos in 2015 and being turned down; Bezos later cited airliners in an Amazon shareholder letter as an example of work only a large company could undertake.

Scholl had no conventional aerospace résumé himself. He was a software engineer who had worked at early Amazon and founded an app company acquired by Groupon. His aviation experience amounted to a pilot’s license and flying a Cessna. He says he could not know in advance whether he was capable of building an airliner. The only way to find out was to choose a mission that mattered to him and work toward it fully.

Boom’s first physical artifact was a cabin mockup made from cardboard, plywood, and Office Depot seats. Its early prototype mockup was still cardboard by the end of Y Combinator. Rather than claim that the company already knew how to build a passenger aircraft, Boom chose a more limited commitment: build a supersonic demonstrator and learn from it.

XB-1, initially called Baby Boom, was intended to become the first supersonic jet developed outside a government or military program. More than a decade after Boom’s founding, it broke the sound barrier in January 2025.

Tristan Brandenburg flew the aircraft. When test control authorized acceleration to Mach 1.1, Brandenburg acknowledged the instruction; controllers then declared XB-1 supersonic.

Scholl presents the flight as evidence that a small company can enter a category historically reserved for governments, militaries, and large aerospace firms. The XB-1 team consisted of 50 people.

Blake Scholl describes the company’s small XB-1 team not as proof that aerospace has become simple, but as evidence that hardware development can be reorganized to behave more like software. The objective is to reduce the cost of iteration in both the world of bits and the world of atoms.

Aircraft are unusually difficult to change because they are tightly integrated. Add another row of seats, he explains, and the fuselage becomes heavier; the engines may need more power; the wings may need redesign; other systems change in turn. In the conventional process he describes, engineering specialists each work in separate spreadsheets, hand analyses from one discipline to another, and eventually stop iterating because the cost of another cycle is too high.

Scholl calls this spreadsheet-centered practice “baby software”: code treated as a second-class artifact, without automated integration, testing, or continuous integration. Boom’s answer is Makeboom, a system that lets engineers define an aircraft in a configuration file and run a whole-aircraft simulation. In minutes, the company can estimate range, fuel burn, payload, passenger capacity, and tradeoffs.

The purpose is not just to assess a selected configuration. A supersonic airliner cannot reach product-market fit by building one and then discovering whether customers like it, in Scholl’s account. The company must first examine the universe of plausible aircraft digitally: what can be built, what combinations of range and capacity are economically useful, and which design has the largest potential market.

The Makeboom chart shown on screen plots nominal mission fuel burn against passenger count, with separate lines for ranges from roughly 3,800 to 4,500 nautical miles. Its significance is not one preferred number on the chart. It makes visible the coupled choice Boom says it must make before cutting metal: adding passengers and extending range each change the fuel-burn outcome, so capacity, range, and operating economics have to be evaluated together rather than optimized independently.

Boom applies the same approach to propulsion through a tool called Blade Runner. Scholl says a small number of engineers can change a turbine-blade design in real time and see its structural and aerodynamic behavior. He contrasts that with a process that would previously have required dozens of engineers and months of work.

The digital system only matters if it connects quickly to physical testing. Scholl says iteration through outside aerospace suppliers is too slow, so Boom built its own machine shop. In its Denver R&D facility, a digitally designed engine component can become a prototype part in roughly 24 hours. Engineers and manufacturing technicians work together, allowing ideas to become physical parts in hours rather than wait through a supplier queue.

Boom is also building its own engine test stand near its engineering and manufacturing operation. The advantage is scheduling control: when a component is ready, the company can test it rather than wait for capacity at someone else’s test cell.

This is vertical integration as a feedback system, not simply a preference for owning more assets. Scholl says Boom’s eventual factory is meant to produce engines and later aircraft at scale. The building had been empty when Boom signed its lease in January; six months later, machines were being installed, with first production engine parts expected within weeks.

Blake Scholl describes an airliner as a financing problem as much as an engineering problem. Development requires billions of dollars in research and development, but neither the total capital requirement nor the timeline can be known precisely in advance.

Boom’s choice to develop its own propulsion system created a separate route to data, reliability learning, and revenue. The company adapted its supersonic engine into a natural-gas power turbine for ground generation, called Superpower. Unlike the complete passenger aircraft, that product can ship on its own.

The ground-power turbine can generate test data, demonstrate reliability, and supply capital while the airliner remains under development. The first Superpower turbine was under construction at the time of the presentation, with delivery to its first customer expected in less than 12 months.

The same orientation informs Scholl’s account of manufacturing competition with China. He does not think the United States can win by trying to recreate every labor-intensive category of production that moved abroad. The objective should instead be to invent the next manufacturing wave and build that domestically.

His example is tool-and-die work: the precision molds, tools, and fixtures needed to make specific hardware parts. Scholl says much of that industry migrated to China and became difficult to find in the United States. Boom’s response is not to depend on rebuilding the same tooling base. For turbine blades, it is exploring an all-digital manufacturing process intended to move from a digital design to an advanced blade in 24 hours with no tooling.

AI, in Scholl’s account, helps chiefly because it lowers the cost of building the software needed to run this kind of operation. He points to Amazon, where he began working in 2001. Amazon built its own recommendation systems, warehouse systems, delivery software, and backend operational tools. He argues that the company gained an advantage because the software fit its own business “like a glove.”

At the time, that level of custom development required a large company. AI makes more specialized internal tools affordable for smaller organizations and lets users of internal systems increasingly become tool builders themselves.

Scholl does not describe this as solved physical-world automation. CNC programming remains highly manual, he says, and he has not yet seen much industrial AI that works despite many pitches. But he sees no fundamental reason a manufacturing system could not eventually take a CAD design and output an automatically quality-assured part without a programmer.

Nor does he believe cheaper software development eliminates demand for software engineers. At Boom, lower software costs have increased the company’s need for engineers because it can now build more internal tools. Hardware engineers may write more code, but software specialists remain necessary to make the architectures coherent.

Blake Scholl says founders must optimize for two days: the worst day and the best day. The first is inevitable; the second is why the work must matter enough to survive the first.

Boom nearly failed several times before XB-1’s supersonic flight. At one point, Scholl says, the company had seven days of cash remaining and its board told him to shut it down. He refused, believing the company had not yet found its way through rather than believing no path existed.

The best day was watching the team pull the aircraft out of the hangar, seeing the pilot advance the throttles, and watching XB-1 break the sound barrier. The contrast is central to Scholl’s view of founder motivation: a company needs to make something important enough to its founders and to the world that they can continue when closure seems rational.

He is explicit that Boom’s financing path is not a model to copy wholesale. It took more time and more money than he expected even to reach a real proof of concept. With hindsight, he says, Boom was early to deep tech and should have planned a simpler initial prototype with multiple shots on goal.

The important hardware iteration is at the product level. A smaller, easier prototype can reveal not only engineering errors but incorrect requirements. More early proof points would have enabled faster learning and made fundraising easier. Scholl’s advice is therefore not to imitate XB-1’s scale of ambition; it is to design a sequence of experiments that gives a company repeated chances to learn.

Blake Scholl frames hiring, self-education, and founder confidence as versions of the same problem: finding people who will confront reality directly rather than relying on credentials, inherited expertise, or a résumé-shaped idea of what they should do.

Boom operates in an industry with little recent startup history. Scholl says the last entrepreneur-founded company to go on to build a commercial airliner was Douglas Aircraft in 1921. That leaves a startup with a difficult hiring tension: it needs technical competence and useful experience, but it also needs people not overly shaped by the cultures of legacy aerospace companies.

He values early-career people who are ambitious, intelligent, hands-on, optimistic, and already building. For candidates without formal work experience, the relevant proof is a side project or another extraordinary accomplishment. At Boom, he says, a lack of conventional credentials can be offset by evidence that someone has made something real.

That principle is especially important for young engineers trying to enter hardware. Scholl rejects the premise that experience necessarily wins or that barriers are too high for newcomers. Build things, he advises, including as hobbies; someone interested in aircraft can make RC planes. Learn not only to design objects but to make them. The point is contact with physical constraints, not a claim to abstract expertise.

He also warns against treating inexperience as a reason to ignore available knowledge. Boom has a rule: if an engineer is attempting something that another person has already done somewhere in the world, the engineer should find one of those people, call them, and ask for advice. The engineer does not have to take that advice, but must hear it. Scholl says experienced and accomplished people are often more willing to offer that guidance than young builders expect.

His own aerospace education followed a similar discipline. He bought textbooks, returned to physics and calculus through Khan Academy, and worked problem sets. More important, he kept a “confusion list”: concepts he could answer plausibly or pass a test on but did not genuinely understand from first principles.

The list grew rather than shrank, because each answer produced new questions. But it trained him to distinguish understanding from hand-waving. That distinction matters in complex physical work, where a gap in understanding can remain hidden until a part, a system, or a test exposes it.

Scholl’s own path is also the basis for his rejection of advice to work only on what one already knows. His résumé did not point naturally toward a supersonic airliner, and he did not begin with confidence that he could build one. Friends were skeptical; one told him to call back with something less pie-in-the-sky.

The question, in his account, was not whether he was already qualified. It was whether he could direct his energy toward figuring out how to become capable. Nobody gives a founder permission to take on an improbable mission. Self-doubt can remain, but it should not decide whether the work is attempted.

That is why he distinguishes knowledge from care. Skills can be taught and knowledge can be acquired; caring about the work cannot be supplied in the same way. His prior mobile-commerce company aligned with his experience, but he says he did not care about what it was building and therefore lacked product vision.

For Scholl, a company is worth starting when its problem is difficult to put aside: an idea that a founder wants to create despite uncertainty about execution. If that does not yet exist, he recommends working with the strongest people available on a problem that matters to the organization and that the individual wants to solve.

He describes his early Amazon experience in those terms. At 23 or 24, he says, he had responsibility for a $300 million P&L attached to a project that mattered to Jeff Bezos and to Amazon. The useful early-career intersection is work a person loves, can become good at, and that matters to the organization around them.

This preference for meaningful work also informs Scholl’s view of work-life balance. He favors “work-life harmony”: work that matters is part of life rather than its opposite. Starting Boom while raising three children under two was difficult, he says, but possible. His conclusion is not that commitments disappear when work is ambitious, but that people should avoid allowing work and obligations they do not value to consume their energy.