Y Combinator · Startup School 2026

“The Future Was Supposed to Be Faster”

The Boom Supersonic founder explains why aviation stalled for 50 years — and how a cardboard mock-up became the first privately built jet to break the sound barrier.

Y Combinator · 50 min · brief by The Daily Read

50 min

Runtime

2014

Founded

Mach 1.1

XB-1 top speed

Millions

Livestream viewers

Tap a timestamp pill below to jump the video to that moment.

The problem

Why the world stopped getting faster

Blake Scholl opens with the line “Houston, we have a problem” — and he means it literally. In 1969, the same year humans walked on the moon, Concorde took its first flight. Half a century later, we can do neither. The moon programme has been cancelled and restarted twice, and the last supersonic passenger service retired in 2003. The future that engineers of that era promised never arrived.

“In 1969, we landed on the moon and the same year we flew Concord…”

I want to start by saying Houston, we have a problem. In 1969, we landed on the moon for the first time and the same year we flew Concord, the faster than the speed of sound airliner. The future was supposed to be faster and better. We were supposed to look forward to innovation in air and in space. And yet, half a century later, we can’t go to the moon and we can’t fly faster than the speed of sound. And not only have we lost the ability to go fast, we’ve lost the ability to do things even at any kind of reasonable speed. It now takes Lockheed more than two years to build a new Patriot missile interceptor. This is crazy. This is no way to build the future and this is no way to win a war.

Scholl makes the stagnation concrete with two slides: a Boeing 707 from the 1960s next to a 787, the newest widebody airliner, launched more than twenty years ago. You cannot spot the difference, he says. The 787 does not fly any faster. It does not make the world any more accessible. The commercial aviation industry spent half a century optimising for seat costs and fuel burn, and in doing so quietly abandoned the goal of going faster.

The same inertia shows up in defence procurement, in spacecraft development, in infrastructure. The problem is not that physics changed — the problem is that the organisations and incentives built around high-stakes hardware became so risk-averse that genuine speed regressed. That is the gap Boom Supersonic set out to close, starting in 2014, not with government funding and not inside an incumbent manufacturer, but as a startup.

How they solve it

From cardboard mock-up to Mach 1.1 — and on to Overture

Boom’s YC application in 2014 included a supersonic airliner mock-up built from cardboard, plywood, and seats sourced from Office Depot. People laughed. Who names an airplane startup after the sound of an explosion? But the team treated ridicule as a filter — only people who could see past the cardboard were the right early customers, partners, and hires — and kept building. The first real prototype, called XB-1, began life as “baby boom,” a one-third-scale demonstrator designed to answer the engineering questions Boom could not answer on paper. Last year, XB-1 became the first independently developed jet to break the sound barrier, hitting Mach 1.1 over the Mojave Desert.

“That’s right. This is a supersonic airliner mockup made of cardboard, plywood and seats from Office Depot…”

That’s right. This is a supersonic airliner mockup made of cardboard plywood and seats from Office Depot. That was before YC. And by the end of YC batch, this is what Boom looked like. Now we had a cardboard mockup of our first airliner prototype. And people laughed. Who would name an airplane startup after the sound of an explosion? But we didn’t let this deter us and we kept going. We started building our first prototype airliner XB-1 which started life as baby boom. We didn’t know what it would really take to build a supersonic passenger plane. And so we figured the only way to learn the lessons was to go build the first supersonic jet made outside of a government or military. And that was how XB-1 got started. Last year, XB-1 became the first independently developed jet to break the sound barrier more than a decade after founding the company.

XB-1 also proved something that had been theorised but never demonstrated at scale: mach cutoff. The sonic boom a supersonic aircraft generates does not always reach the ground. If the airplane is at the right altitude and flying at the right speed relative to the winds, the boom refracts upward and curves back toward the sky before it reaches anyone’s ears. Boom flew XB-1 through the sound barrier six times in two flights and produced no audible boom on the ground — turning what had been the political and regulatory killer of supersonic travel into a solved engineering problem. As Scholl puts it: “It’s like if a tree falls in a forest and no one’s there to hear it.”

“XB-1 broke the sound barrier six times. Each time no audible sonic boom on the ground…”

Which is related to solving sonic boom. XB-1 broke the sound barrier on two flights, six times through the sound barrier. Each time no audible sonic boom on the ground. We actually demonstrated a principle that had been talked about for a long time called mach cutoff where if you break the sound barrier at the right altitude and at the right speed for the current weather, the sonic boom actually makes a U-turn in the sky and never touches the ground. So it’s like if a tree falls in a forest and no one’s there to hear it, did it make a sound? We’re going to find out.

With the physics and prototype work behind them, Boom turned to Overture — the full-size passenger airliner — and immediately hit the second hard problem: financing a hardware programme that will cost billions of dollars and cannot predict its exact timeline. Scholl’s answer was vertical integration. By choosing to build their own engine rather than sourcing one from an incumbent, Boom gained an unexpected revenue stream: the same supersonic engine, adapted slightly, can run as a natural gas power turbine on the ground. Boom calls it Superpower. The first Superpower turbine ships to its first customer in under twelve months, generating test data, manufacturing confidence, and capital — all before Overture has flown a single passenger.

“We discovered that because we had made a choice to vertically integrate our own propulsion…”

It’s very very difficult to raise financing, but we discovered along the way that because we had made a choice to vertically integrate our own propulsion, we were able to take the engine that we were building for supersonic flight and sell it separately on the ground as a natural gas power turbine and that’s what we call Superpower. This is a supersonic engine adapted for ground power generation that can ship without the rest of the airplane, thereby generating the test data, the learnings, the reliability, and also the capital that we need to go big. The first Superpower turbine under construction right now goes to the first customer in less than 12 months. So let’s take a step back and think about why we’re doing this. I think it’s important to create things that we want to exist in the world and I think it’s important to create things that inspire other creators. Because of that, we chose to live stream XB-1’s supersonic flight. This was the first supersonic installation of Starlink, the first supersonic air-to-air live stream. And when we turned that stream on, millions of people around the world tuned in. And some of my favourite shots were from classrooms around the country where kids who were otherwise not tuned in to aviation or to science tuned in and some of them stood up and some of them jumped up and down.

The Superpower move is not an accident of engineering — it is a deliberate strategy that echoes lessons Scholl took from early Amazon. He worked with Jeff Bezos in his early twenties, managing a $300 million P&L at 23 or 24. What he saw Amazon do unusually well was build software that fit the business “like a glove,” creating structural advantages competitors could not replicate by buying off-the-shelf tools. Boom’s vertical integration of propulsion is the hardware equivalent: you cannot buy a supersonic engine; you have to build it. And having built it, you own something nobody else has.

Takeaway

The quick version

Commercial aviation got slower after Concorde — the 787 looks identical to the 707 and does not fly faster. Regulatory risk-aversion and incumbent incentives entrenched the stagnation.
Boom solved the two showstopper problems: sonic boom (mach cutoff lets the boom U-turn before it hits the ground) and financing (sell the supersonic engine as a ground turbine to fund the airplane).
XB-1 breaking the sound barrier as the first independently built jet to do so proves that ambitious hardware can be developed outside government programmes — if founders are willing to build the sub-scale demonstrator first.
If something is calling you, start building. Scholl’s advice: self-belief comes late, from doing the work — not from feeling ready in advance.

“I think it’s important to create things that we want to exist in the world and I think it’s important to create things that inspire other creators.”— Blake Scholl, Boom Supersonic

The flight path from cardboard mock-up to Mach 1.1 took twelve years and ran through every constraint that stops most founders. Scholl’s point isn’t that the obstacles weren’t real — it’s that they were learnable, one prototype at a time.