The ‘Mystery’ YF-118G: Bird of Prey Stealth Aircraft No One Knows About

Article Summary – Developed in secret at Area 51 in the 1990s, the McDonnell Douglas/Boeing YF-118G Bird of Prey was never meant for combat.

-Instead, this one-off stealth demonstrator proved the U.S. could field cutting-edge low-observable tech on a shoestring budget.

Boeing X-32 Fighter at USAF Museum July 2025. Image Credit: National Security Journal.

-Built for just $67 million with off-the-shelf parts and single-piece composite structures, the slow, low-flying testbed focused on radar invisibility, not performance.

-Its blended wing-body, shielded intake, and “gapless” control surfaces validated design and manufacturing techniques later used on the X-32 and X-45 programs.

-After 38 flights, the Bird of Prey retired to the Air Force museum—but its stealth legacy lives on.

Inside the YF-118G Bird of Prey: Boeing’s $67 Million Stealth Test Jet From Area 51

The McDonald Douglas Phantom Works designed an amazing stealth aircraft that Boeing built in the 1990s. This was the YF-118G Bird of Prey. It was developed at Area 51.

It was never intended for operational service, but 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.

The aircraft was named after the Klingon Bird of Prey from the Star Trek franchise due to its outward appearance, which mimicked the Star Trek spacecraft. The aircraft minimized radar cross-section with its blended-wing-body configuration, shielded engine intake, and “gapless” control surfaces.

The Bird Of Prey Stealth Aircraft Changed Aviation:

The Boeing YF-118G Bird of Prey was a revolutionary experimental aircraft developed in the 1990s 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. 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.

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 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.

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).

An F-15E Strike Eagle stands static on the flightline before morning takeoffs at Royal Air Force Lakenheath, England, Jan. 5, 2021. The 48th Fighter Wing conducts daily flying operations in order to ensure the Liberty Wing can deliver unique air combat capabilities when called upon by its NATO allies. (U.S. Air Force photo by Senior Airman Madeline Herzog)

Stealthy Airframe and Spare Parts

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.

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 (see image at the end of this article) demonstrators and later in its X-45A Unmanned Combat Air Vehicle prototype.

Boeing X-32 Fighter USAF Museum Dayton Ohio. Image Credit: National Security Journal.

Boeing X-32 Fighter at USAF Museum July 2025. 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.

“The Bird of Prey, however, used some ‘off the shelf’ technology to reduce costs and speed production. Its control system is all-manual with no computer assists, and the landing gear is adapted from Beech King Air and Queen Air aircraft.”

Air Force Test pilot Colonel Doug Benjamin once joked, “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 1998.

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.

YF-118G USAF Museum. Image Credit: National Security Journal.

The YF-118G Bird of Prey was only a single plane, but it paved the way for the stealth aircraft of today.

About the Author: 

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.