The US Federal Aviation Administration (FAA) has granted Hermeus authorization to conduct flight tests above Mach 1 with its experimental Quarterhorse Mk 2.1 aircraft, marking a regulatory step for the startup’s high-speed development program.
The approval, effective April 9, allows Hermeus to perform up to seven supersonic flights through the end of 2026. Tests will take place over the White Sands Missile Range in New Mexico, within restricted military airspace and at altitudes above 30,000 ft.
Hermeus had filed the request in January, seeking a special flight authorization under US regulations that generally prohibit civil aircraft from exceeding the speed of sound over land. The FAA concluded the proposal complies with existing rules and does not pose significant environmental impact, relying on prior studies conducted for operations at the test range.
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The Quarterhorse Mk 2.1 is an uncrewed experimental aircraft designed to validate systems and aerodynamic performance at high speed. It completed its first subsonic flight in March and is powered by a Pratt & Whitney F100 engine, commonly used in fighter jets.
The platform is the first in a series of progressively more capable demonstrators. Hermeus plans to use the Mk 2.1 to cross the Mach 1 threshold, followed by the Mk 2.2 and Mk 2.3 variants, which are intended to reach higher speeds, including the Mach 3 range.
These aircraft serve as stepping stones toward the company’s longer-term objective: a reusable vehicle capable of sustained hypersonic flight above Mach 5. Unlike some competing concepts that rely on rocket propulsion and carrier aircraft, Hermeus is pursuing a design that can take off and land conventionally, combining a turbofan engine with a dual-mode ramjet for operation across different speed regimes.
The FAA authorization removes a key regulatory barrier for early testing, allowing the company to begin gathering real-world data on supersonic flight characteristics, propulsion integration and autonomous control systems.
The development effort is also being supported by fresh capital. Earlier in April, Hermeus announced a $350 million Series C funding round led by Khosla Ventures, aimed at accelerating the Quarterhorse program and expanding its aircraft fleet. The investment will fund the next test vehicles and support the company’s expansion in Los Angeles, while production activities remain in Atlanta.
