Key Points and Summary – Built in secrecy at Area 51 in the 1990s, Boeing’s YF-118G “Bird of Prey” was a low-cost stealth demonstrator that flew just 38 sorties before the Pentagon revealed it in 2002.
-Costing $67 million, the jet relied on off-the-shelf parts—Beech King/Queen Air gear, a Pratt & Whitney JT15D-5C, a Harrier ejection seat (and, as one pilot joked, a Wal-Mart clock)—to prove ideas cheaply.
YF-118G Bird of Prey at USAF Museum 2025. Image Credit: Harry J. Kazianis/National Security Journal.
-Its single-piece composite body, blended wing-fuselage, shielded intake and “gapless” control surfaces slashed signatures and pioneered disposable tooling.
-The lessons fed directly into the X-32, F-22, F-35 and X-45 programs. The prototype resides at the USAF Museum.
The YF-118G Bird Of Prey: How Was It Kept Secret?
The YF-118G “Bird of Prey” was arguably one of the most unique, best-looking aircraft ever built. If you think it resembled a sci-fi spacecraft from Hollywood, you would not be wrong.
McDonald Douglas’ Phantom Works designed an amazing stealth aircraft, the YF-118G, also known as the Bird of Prey, which Boeing built in the 1990s. The aircraft was developed at Area 51.
The program was a huge success, and the lessons learned paved the way for future stealth aircraft, such as the X-32, the F-22, and the F-35, as well as the X-45 unmanned combat drone, which forever changed aircraft design.
The service never intended it for operational service, but rather to test the limits of stealth technology at a low cost. Boeing transitioned from a paper design to building the aircraft using off-the-shelf parts for less than $67 million. That’s less than the cost of a single F-35 stealth fighter.
A U.S. Air Force F-35A Lightning II, from the 421st Expeditionary Fighter Squadron, deployed to Kadena Air Base, taxis after a training mission at Kadena Air Base, Japan, July 11, 2025. The F-35 is an agile, versatile, high-performance, multirole fighter that combines stealth, sensor fusion and unprecedented situational awareness to overcome adversarial and situational challenges. (U.S. Air Force photo by Airman Nathaniel Jackson)
The aircraft was named after the Klingon Bird of Prey from the Star Trek franchise, due to its outward appearance that mimicked the Star Trek spacecraft. The aircraft minimized radar cross-section with its blended-wing-body configuration, shielded engine intake, and “gapless” control surfaces.
How did Boeing keep the aircraft secret for so long? And how were they able to build it so cheaply?
How Boeing Kept It Under Wraps
During the period when the YF-118G was being tested, from 1992 to 1999, the Air Force already had the F-117 stealth fighter (which wasn’t a fighter at all) and the B-2 Spirit bomber was already in development.
The Bird of Prey was a further development of stealth technology for future designs. But due to its location at the secret US site known as Area 51, it lent itself to keeping the aircraft’s development a secret.
The Air Force ran the program in complete secrecy from 1992 to 1999, with the first flight taking place in 1996. The Pentagon acknowledged the existence of the Bird of Prey in 2002, but only after much of its stealth technology had been incorporated into other aircraft, such as the X-32 Joint Strike Fighter (the future F-35) and the X-45A Unmanned Combat Air Vehicle.
Boeing X-32 Full View. Image Credit: National Security Journal.
A Sideview of the Boeing X-32 JSF. Image Credit: Harry J. Kazianis/National Security Journal.
The aircraft made only 38 test flights between 1996 and 1999, limiting the number of opportunities for it to be observed. But the company did a great job of keeping the aircraft’s secrecy under wraps.
Unique Blend of Spare Parts
In an incredible show of resourcefulness and frugality, Boeing saved a boatload of money by building the Bird of Prey out of spare parts.
To expedite development and minimize expenses, the aircraft utilized existing, non-specialized components.
Examples include the landing gear, which was adapted from a Beech King Air and Queen Air aircraft; a single commercial Pratt & Whitney JT15D-5C turbofan engine; an ejection seat from a Harrier; and cockpit controls from various existing tactical aircraft.
One test pilot even joked that the clock was from a retail store.
The Bird Of Prey Was A Game Changer
The Boeing YF-118G Bird of Prey was a revolutionary experimental aircraft developed as a platform to explore and refine stealth technology.
This single prototype demonstrated that Boeing could rapidly bring an effective stealth platform to the prototyping phase, helping the United States and NATO maintain a qualitative technical edge over peer and near-peer adversaries.
The most significant contribution this incredibly unique aircraft has made to America’s defense apparatus was in its boldness and subsequent success.
The body was constructed from a single piece of composite material, which eliminated the ridges and seams of traditional aircraft that create radar reflections.
While most stealth programs are known for their high cost, the Bird of Prey transitioned from design to flight over Area 51 for less than the cost of a single F-35 today.
The Bird of Prey was powered by a Pratt & Whitney JT15D-5C engine; it was far from a performance giant in terms of speed and altitude. Its cruising speed was just 300 miles per hour; the stealthy aircraft was slower than a C-130 Hercules, and its maximum operational ceiling was 20,000 feet. But the designers weren’t looking for a hot rod, but for near invisibility on radar.
When the United States started producing the F-117 Nighthawk in 1983, it too was far from as fast as the existing fighters of the day. But the Nighthawk wasn’t a fighter, but a nearly invisible attack aircraft.
F-117 National Security Journal Photo Taken at U.S. Air Force Museum.
F-117 Stealth Fighter Original National Security Journal Photo.
US-made F-15s and F-16s had a radar cross-section of 82 square feet; the F-117 carried a radar cross-section of only slightly more than a tenth of an inch (0.11 inches).
The radar cross section (RCS) was estimated to be as small as a mosquito. Engineers also placed the powerplant deep within the fuselage to minimize its infrared signature. They carefully designed the paint shading to mask the actual fuselage shapes in daylight visually.
Stealthy Airframe and Spare Parts
Ultimately, the entire program reportedly cost $67 million, less than the cost of two new 737s at that time.
The Boeing design team used single-piece composite structures and disposable tooling. In the final specification, the aircraft measured 47 feet in length, with a wingspan of 23 feet, and a curb weight of approximately 7,400 pounds.
“In its 38 flights, the Bird of Prey tested ways to make aircraft less observable to the eye and to radar,” the U.S. Air Force said. “It also validated new ways to design and build aircraft using large single-piece composite structures, “virtual reality,” computerized design and assembly, and disposable tooling.
“The Bird of Prey was revealed in 2002 because its design techniques had become standard practice — Boeing used them in its X-32 Joint Strike Fighter demonstrators and later in its X-45A Unmanned Combat Air Vehicle prototype.
F-22A Raptor with YF-118G Overhead. Image Credit: National Security Journal.
YF-118G above and F-22 Raptor Below. Image from National Security Journal.
YF-118G Flying High July 2025. Image Credit: National Security Journal.
YF-118G Bird of Prey Hanging Above F-22. Image Credit: National Security Journal.
“The aircraft demonstrates advanced stealth concepts, notably its “gapless” control surfaces that blend smoothly into the wings to reduce radar visibility, and an engine intake completely shielded from the front.
An effort was made to reduce the cost of the aircraft by using off-the-shelf components wherever possible. By selecting an off-the-shelf Pratt and Whitney JT15D-5C turbofan jet engine, landing gear from Beechcraft turboprops, an ejection seat from a Harrier, and cockpit controls from various existing tactical jets, the team scavenged scrap yards and kept the total cost under control.
Air Force Test pilot Colonel Doug Benjamin once joked that “the clock was from Wal-Mart and the environmental control system was essentially a hairdryer.”
After the Bird of Prey flew 38 test flights between 1996 and 1999, the program was successful enough to survive the acquisition of McDonnell Douglas by Boeing in 1997.
The program was publicly unveiled in late 2002, and the aircraft was given to the National Museum of the United States Air Force in Dayton, Ohio, where it remains on display today.
And, in fact, many of the photos in this article come from our most recent visit to the YF-118G back in July.
About the Author: Steve Balestrieri
Steve Balestrieri is a National Security Columnist. He served as a US Army Special Forces NCO and Warrant Officer. In addition to writing on defense, he covers the NFL for PatsFans.com and is a member of the Pro Football Writers of America (PFWA). His work was regularly featured in many military publications.
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