Pratt & Whitney Licenses Hermeus to Build F100-PW-229 Fighter Engines

Pratt & Whitney, an RTX business, and defense aviation company Hermeus announced a Production License Agreement on September 15, 2026, authorizing Hermeus to manufacture the F100-PW-229 fighter engine. The agreement, datelined Los Angeles, creates a new qualified production source for what the companies describe as one of the U.S. military’s most widely fielded fighter propulsion systems.

Under the agreement, Hermeus will produce the engines using its rapid-build production model while adhering to Pratt & Whitney’s global standards for quality, safety and site-activation. The companies stated the arrangement strengthens the U.S. defense industrial base, accelerates production of the F100-powered Quarterhorse aircraft and expands U.S. capacity to build fighter engines.

“With more than 32 million flight hours, the F100 has earned its place as one of the world’s most trusted fighter engines,” said Jessica Villardi, vice president of Fighter & Mobility Programs at Pratt & Whitney. “By partnering with Hermeus, we are expanding U.S. production capacity to meet growing customer demand while delivering the proven dependability that defines the F100 engine.”

“Meeting future operational needs requires expanding America’s capacity to build the engines our warfighters rely on,” said Zach Shore, CEO of Hermeus. “Pratt & Whitney built the standard for fighter propulsion. By becoming a licensed manufacturer of the F100, Hermeus expands domestic engine capacity for the broader defense industrial base and becomes the first vertically integrated airframer with the in-house propulsion capability required to scale Quarterhorse.”

Hermeus also published the same announcement on its own newsroom on September 15, 2026. In that copy, Shore’s statement instead characterizes Hermeus as one of the few vertically integrated airframers with the in-house propulsion capability required to scale Quarterhorse, rather than the first.

The announcement notes that the F100 powers Hermeus’ Quarterhorse aircraft, which achieved supersonic flight earlier in 2026, and the companies characterize it as the world’s first privately developed unmanned supersonic jet. The F100 has powered the U.S. Air Force’s F-15 and F-16 fighter jets for more than five decades.

F100 Fleet and Specifications

Pratt & Whitney’s official F100 product page lists more than 3,800 F100 engines in 23 air forces around the world, with more than 30 million flight hours flown. The company states the F100 is currently in production and that it is committed to supporting the fleet for decades to come, including in the F-15EX and new F-16s. The page also notes the F100-PW-229 is fully capable of integrating with the F-15EX, that support systems are already in place at F-16 and F-15 bases around the world, and that the engine incorporates fifth-generation technology in a fully modular architecture.

The page’s published specifications for the F100-PW-229 list 29,160 pounds (129.7 kN) of thrust, a maximum weight of 3,826 pounds (1,735 kg), a length of 191 inches (4.85 m), an inlet diameter of 34.8 inches (0.88 m), a maximum diameter of 46.5 inches (1.18 m), a bypass ratio of 0.36, an overall pressure ratio of 32 to 1 and a thrust-to-weight ratio of 7.6.

Pratt & Whitney’s recorded F100-PW-229 milestones include the first production delivery in December 1989, a successful field service evaluation in September 1990 and the first operational introduction in April 1992. The engine completed a 6,000 TAC Accelerated Mission Test in September 2010, the F100 fleet surpassed 28 million engine flight hours in July 2018, and the first F100-229 achieved 6,000 TACs in February 2020.

Quarterhorse Program and F100 Testing

The licensing agreement follows a series of F100 milestones in Hermeus’ Quarterhorse test program. In a May 26, 2026 announcement, Hermeus said Quarterhorse Mk 2.1 completed its first supersonic flight, reaching a top speed of Mach 1.21 on its third test flight out of Spaceport America over White Sands Missile Range airspace. The F-16-scale aircraft is powered by the Pratt & Whitney F100, and Hermeus said it flew supersonic less than three months after its first flight and 364 days after the maiden flight of the company’s first aircraft, Mk 1.

Mk 2.1 is the first of three F-16-scale supersonic aircraft in Hermeus’ development roadmap. The company said it is already building and testing Quarterhorse Mk 2.2, with Mk 2.3 soon to follow, and that each aircraft in the roadmap is designed to push performance further toward sustained high-Mach flight.

Hermeus has also run the F100 on the ground. The company said it brought its High Enthalpy Air-Breathing Test Facility (HEAT) at Cecil Airport in Jacksonville, Florida online with a series of F100 engine tests, reusing test infrastructure from the former Cecil Naval Air Station, including multiple test cells originally built in 1959 and an aircraft hush house from 1989. Hermeus said the facility came online three months after breaking ground.

In that earlier announcement, Hermeus said the F100 tested at HEAT would be utilized in Quarterhorse Mk 2 and that, paired with the company’s proprietary precooler engine technology, the aircraft would be capable of speeds greater than Mach 2.5. The company also said the F100 will serve as the turbine core of Chimera, a turbine-based combined cycle engine it describes as capable of reaching Mach 5. Chimera is planned to power Quarterhorse Mk 3, which Hermeus said is being designed to demonstrate turbine-to-ramjet mode transition in flight and, in doing so, break the air speed record held by the SR-71.