Boeing YF-118G Bird of PreyBoeing YF 118G Bird of Prey airplane model. The Bird of Prey was a black project aircraft intended to demonstrate stealth technology. Fully paid for by company funds at a price of $67 million (as opposed to the government sponsored norm), it was a very cost effective program, developing technology and materials which would later be used on Boeing's X 45 UCAV. As an internal project, this aircraft was not given an X plane designation. The Bird of Prey