YF-118G 'Bird of Prey': The Stealth Aircraft That History Forgot About

Summary: The U.S. Air Force is finalizing tests on the B-21 Raider and has approved its full-scale production, even as plans for its successor are presumably underway. This proactive approach exemplifies the military's strategy to maintain technological superiority. A key example of such forward-looking efforts was the YF-118G Bird of Prey, a Boeing-built stealth technology demonstrator active from 1992 to 1999.

-Although not designed for speed, the Bird of Prey played a crucial role in advancing stealth technologies that influenced later aircraft like the F-22 and F-35.

-This ongoing cycle of innovation ensures that the U.S. military remains at the cutting edge of aerospace technology.

Here Comes the YF-118G

The U.S. Air Force is conducting final testing on its B-21 Raider strategic bomber prototypes, and the Pentagon has given the green light for full-scale production of the stealth bomber. 

Even with the aircraft awaiting its entry into operational service, it is extremely likely that in some small offices and test labs, the military is already working on the B-21 Raider’s eventual replacement.

That has nothing to do with the capabilities and attributes of the B-21 Raider. It is just the way the U.S. military works in order to stay ahead of global competition.

Military and defense companies often create technology demonstrators that end up influencing the design, development, and production of numerous weapons systems.

Probably the least known but most impactful of these technology demonstrators was the YF-118G Bird of Prey.

Stealth Flying YF-118G 

Designed and built by Boeing, the YF-118G was a highly classified demonstrator designed as a testbed for the stealth technologies that would become operational in future fighter and bomber aircraft.

At the time of the Bird of Prey’s use, the U.S. Air Force was already flying the first-ever operational stealth aircraft, the F-117 Nighthawk stealth bomber. The B-2 Spirit stealth strategic bomber was coming online. Boeing and the Air Force sought to further test stealth technology for future generations of low-observable aircraft. It is likely that the knowledge gained and the technology developed from the YF-188G Bird of Prey’s test flights influenced aircraft like the F-22 Raptor and F-35 Lightning II stealth fighter jets.

The YF-118G was powered by one Pratt & Whitney JT15D-5C turbofan engine, which could produce a little over 3,000 lbs of thrust and speeds of 300 miles per hour. The tech demonstrator wasn’t fast, but speed was not its goal. 

The stealth tech demonstrator was named for a warship in the Star Trek space series. The Air Force ran the program in complete secrecy from 1992 to 1999, with the first flight taking place in 1996. The Pentagon ended up acknowledging the existence of the Bird of Prey in 2002, but only after much of its stealth technology had shown up in other aircraft like the X-32 Joint Strike Fighter (the future F-35) and the X-45A Unmanned Combat Air Vehicle. 

A word about stealth: Aircraft like the YF-118G obviously are not invisible to the naked eye. In fact, they look much like normal aircraft. What qualifies them as stealth planes is their low observability to radar systems. This is achieved through a combination of design, countermeasures, special paints, and sensors. 

The YF-118G Bird of Prey was a short-lived program, but the technology and capabilities it helped develop live today through the number of aircraft it influenced. And who knows – the Air Force likely has a similar technology demonstrator now testing the weapons systems and stealth capabilities of tomorrow.

About the Author

Stavros Atlamazoglou is a seasoned defense and national security journalist specializing in special operations. A Hellenic Army veteran (national service with the 575th Marine Battalion and Army HQ), he holds a BA from the Johns Hopkins University, an MA from the Johns Hopkins’ School of Advanced International Studies (SAIS). He is pursuing a J.D. at Boston College Law School. His work has been featured in Business Insider, Sandboxx, and SOFREP.