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

Key Points and Summary: The Boeing YF-118G Bird of Prey was a revolutionary experimental aircraft developed in secret at Area 51 during the 1990s to test next-generation stealth technologies at a low cost.

-Built by McDonnell Douglas’s Phantom Works for just $67 million, it utilized off-the-shelf parts like its engine and landing gear.

-While slow and low-flying, its primary goal was not performance but near-invisibility to radar, achieved through a “gapless,” blended-wing-body design.

-The 38 test flights successfully validated new design and manufacturing techniques, which were later used on Boeing’s X-32 JSF and X-45 UCAV prototypes.

Boeing X-32B. The Boeing Joint Strike Fighter X-32B demonstrator lifts off on its maiden flight from the company’s facility in Palmdale, Calif. Following a series of initial airworthiness tests, the X-32B, with Boeing JSF lead STOVL test pilot Dennis O’Donoghue at the controls, landed at Edwards Air Force Base, Calif. The X-32B will complete a number of flights at Edwards before moving to Naval Air Station Patuxent River, Md., for the majority of STOVL testing. The overall flight-test program will include approximately 55 flights totaling about 40 hours.

Boeing’s YF-118G Bird Of Prey, The Amazing Stealth Aircraft

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.

Two U.S. Air Force F-35A Lightning II aircraft, with the F-35 Demonstration Team, approach a U.S. Air Force KC-135 for in-flight refueling en route to their next airshow at Pensacola, Florida, on 28 October, 2024. The F-35 Demo Team travels to various bases to showcase the capabilities of the most advanced 5th generation fighter aircraft. (U.S. Air Force photo by Senior Airman Nicholas Rupiper)

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).

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 demonstrators and later in its X-45A Unmanned Combat Air Vehicle prototype.

“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.”

An F-35A Lightning II, assigned to the 388th Fighter Wing, at Hill Air Force Base, UT, flies in formation with a Belgian Air Force F-16 Fighting Falcon on Sept 10, 2022, Kleine Brogel Air Base, Belgium. The F-35 Demo Team consists of approximately 15 total Airmen to include the pilot and commander, pilot safety officers, superintendent, team chief, maintenance Airmen, aircrew flight equipment specialists, and public affairs personnel. (U.S. Air Force photo by Staff Sgt. Thomas Barley).

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.

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.

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