An American aerospace company has broken the sound barrier for the first time as a private firm. Hermeus flew its Quarterhorse Mk 2.1 aircraft to Mach 1.21 on 26 May 2026. It was only the jet’s third test flight.
The flight took place over White Sands Missile Range in New Mexico. The aircraft took off from Spaceport America, a rocket launch site in the same state. Hermeus reached supersonic speed in fewer than three months after the jet’s first flight.
Mach 1 is the speed of sound. At sea level, this is about 1,225 kilometres per hour. Mach 1.21 means the aircraft flew 21% faster than the speed of sound. Engineers and pilots call this “supersonic” flight. You can sometimes hear a loud “boom” on the ground when an aircraft breaks the sound barrier.
The Quarterhorse Mk 2.1 is an unmanned aircraft — there is no pilot on board. It is powered by a Pratt & Whitney F100 engine. This is the same engine that powers the US Air Force’s F-16 fighter jet. The aircraft is about the same size as an F-16.
Hermeus is already building two more aircraft: the Mk 2.2 and the Mk 2.3. Each new design is meant to fly faster than the last. The company’s final goal is hypersonic flight — flying at five times the speed of sound or more.
This is a historic moment for aviation. No private company in the United States had ever flown a supersonic aircraft before. The US military achieved supersonic flight in the 1940s and 1950s, but that was funded by the government. Hermeus did it as a private business.
Hermeus hopes that its technology could one day help create faster passenger aircraft. A future supersonic airliner could cross the Atlantic Ocean in just a few hours.
Key vocabulary:
- sound barrier – the speed of sound, which aircraft must push through to fly supersonically; pilots talk about “breaking” it when an aircraft first reaches this speed
- Mach number – a way of measuring speed compared to the speed of sound; Mach 1 equals the speed of sound, Mach 2 equals twice the speed of sound, and so on
- unmanned aircraft – an aircraft that flies without a human pilot on board; it is controlled remotely or by a computer
CEFR Level B1 / ICAO Level 4