The YF-118G Bird of Prey ‘Stealth Fighter’ Has a Message for the U.S. Air Force

 Key Points and Summary

-Before the F-35, a top-secret program at Area 51 called the YF-118G "Bird of Prey" quietly revolutionized stealth technology.

-Developed by McDonnell Douglas in the 1990s on a shoestring budget of just $67 million, this unconventional, tailless aircraft was a testbed for innovative stealth shaping and cost-effective manufacturing.

-Though it was never intended for combat, the lessons learned from the Bird of Prey's 38 test flights proved invaluable.

-Its design principles directly influenced future programs, including the X-45A combat drone, and helped prove that advanced stealth aircraft could be built quickly and affordably.

-National Security Journal visited the YF-118G back in July of this year. All pictures below are from that visit.

Meet the YF-118 Bird of Prey Stealth Fighter

Before the F-35 took its first flight, Boeing was running experiments on fifth-generation technology using a small testbed aircraft. This test fighter, the YF-118G “Bird of Prey,” conducted several test flights in the late 1980s to evaluate various stealth features and demonstrate that stealth technology could be made cost-effectively.

Despite its relatively obscure place in aviation history, the YF-118G program left a significant mark on the industry.

It proved the importance of stealth shaping and helped the industry cost-effectively create stealth materials.

Creation of the Bird of Prey

The origins of the Bird of Prey can be traced back to a period of intense competition and transformation in the U.S. aerospace industry.

In the late 1980s and early 1990s, McDonnell Douglas was facing increasing pressure to remain competitive after losing major defense contracts, including the Advanced Tactical Fighter (ATF) program to Lockheed Martin’s YF-22, which would become the F-22 Raptor.

In response, McDonnell Douglas initiated a black project under its Phantom Works division, located at the highly classified Groom Lake facility, more commonly known as Area 51.

The project began in 1992 and was funded internally, with a remarkably low budget of just $67 million. This was a strategic move to demonstrate the company’s continued relevance in cutting-edge aerospace technology and to test new concepts that could be applied to future aircraft.

The aircraft was given the designation YF-118G and was nicknamed the "Bird of Prey," a reference to the Klingon spacecraft from the Star Trek franchise. This name was fitting, considering the unconventional layout of the aircraft.

The Bird of Prey featured a tailless, blended wing-body configuration that contributed to its low radar cross-section.

It had a wingspan of 22.8 feet and a length of 46.8 feet. The aircraft was powered by a single Pratt & Whitney JT15D-5C turbofan engine, the same type used in business jets like the Cessna Citation V.

This engine produced 3,190 pounds of thrust, giving the Bird of Prey a top speed of around 260 knots and a service ceiling of 20,000 feet.

A Testbed for Stealth Technology

Despite its modest performance, the Bird of Prey was never intended to be a high-speed or high-altitude aircraft.

First and foremost, the plane was a testbed for experimenting with stealth technologies and innovative manufacturing methods.

The aircraft incorporated several stealth features, including a shielded engine intake, a diamond-shaped exhaust to reduce infrared signature, and seamless control surfaces that blended into the wings.

These design elements helped minimize the aircraft’s radar and infrared signatures, making it difficult to detect.

The YF-118G program sought to prove that advanced stealth fighters could be manufactured in a way that is both efficient and cost-effective.

The aircraft was built using commercial off-the-shelf components, such as landing gear adapted from Beechcraft turboprops and manual hydraulic controls instead of more expensive fly-by-wire systems.

Engineers also utilized virtual reality tools and disposable tooling to expedite the design and manufacturing processes.

These methods allowed the team to iterate quickly and keep costs low, demonstrating that advanced stealth technology could be developed without the need for billion-dollar budgets.

The Bird of Prey made its first flight in September 1996 and completed a total of 38 test flights before the program concluded in 1999.

The aircraft remained classified until October 2002, when Boeing, which had acquired McDonnell Douglas in 1997, publicly unveiled it. By that time, the technologies tested on the Bird of Prey had already been integrated into other programs, and the aircraft’s role as a technology demonstrator had been fulfilled.

Lessons Learned from the YF-118G

Despite the aircraft’s relatively obscure status, the Bird of Prey helped immensely with the development of future stealth aircraft. One of the most important takeaways was the importance of stealth shaping principles.

The aircraft demonstrated that careful shaping of the airframe could significantly reduce radar cross-section, a concept that has since become standard in stealth aircraft design. Additionally, the use of large, single-piece composite structures and simplified manufacturing techniques influenced the way modern aircraft are built, both in the military and commercial sectors.

Many of these design choices undoubtedly made their way into the F-35 and other stealth prototypes. Today, these principles are common practice, but during the 80s, stealth was still relatively new.

Thanks to the Bird of Prey, many of these lessons were learned early and helped give the U.S. the necessary experience in developing fifth-generation technology.

The program did not directly influence the F-22 or B-2 Spirit, but the lessons learned helped influence production work on these aircraft, thereby reducing costs.

Stealth Technology at a Lower Cost

The Bird of Prey also played a key role in the development of unmanned aerial vehicles (UAVs). Its tailless, stable design and stealth features directly influenced the Boeing X-45A Unmanned Combat Air Vehicle (UCAV), which was one of the first stealthy UAVs developed for combat roles. The design philosophy and technologies pioneered by the Bird of Prey helped pave the way for a new generation of unmanned systems that are now integral to modern military operations.

Traditionally, military aircraft programs were characterized by long development cycles and high costs.

The Bird of Prey demonstrated that it was possible to develop and test advanced technologies quickly and affordably by embracing agile development practices and leveraging commercial components.

This approach has since been adopted more widely across the aerospace industry, leading to faster innovation and more cost-effective solutions.

About the Author: Isaac Seitz

Isaac Seitz, a Defense Columnist, graduated from Patrick Henry College’s Strategic Intelligence and National Security program. He has also studied Russian at Middlebury Language Schools and has worked as an intelligence Analyst in the private sector.