Hermeus, the defense aviation company building the world’s fastest aircraft, has announced its Quarterhorse Mk 2.1 successfully completed its first supersonic flight, reaching a top speed of Mach 1.21. The flight was executed on just its third test flight out of Spaceport America over White Sands Missile Range air space. The achievement underscores Hermeus’ pace of iterative development in aviation. Quarterhorse Mk 2.1 flew supersonic less than three months after its first flight, and 364 days after the maiden flight of Hermeus’ first aircraft, Mk 1.

“Our customers at the Department of War are paying close attention to how fast this program is moving,” AJ Piplica, CEO and Co-founder of Hermeus commented “This flight demonstrates a pace of execution that is extremely rare in modern aviation. Our country’s ability to deliver new asymmetric military capability at scale depends on teams that can solve hard technical challenges quickly. That’s exactly what we’re proving with each test flight we conduct and each new aircraft we build at Hermeus.”

Quarterhorse Mk 2.1 is the first of three F-16-scale supersonic aircraft in a development roadmap built on a foundation of rapid iteration. It is powered by the Pratt & Whitney F100 engine (Pratt & Whitney is an RTX business). Hermeus designs, builds, and flies aircraft in quick succession, using flight test data to improve performance and reduce risk across the program. This approach allows the company to unlock and scale new capabilities in years rather than decades. The company is already building and testing its next aircraft, Quarterhorse Mk 2.2, with Mk 2.3 soon to follow. Each aircraft in the roadmap is designed to push performance further and move quickly toward sustained high-Mach flight. The milestone comes as the Pentagon increases focus on high-speed capability in response to growing competition from near-peer adversaries like China. Faster unmanned aircraft have the potential to shorten response times and bring affordable mass to the most challenging contested environments. Hermeus will continue its flight test campaign with Quarterhorse Mk 2.1 while building subsequent aircraft that will add capabilities and push to higher-speed regimes.