Originally from here

Lampyridae is proof that Europe does have the ability to prototype in complete secrecy. Begun in 1981 and revealed only last year, Lampyridae progressed as far as wind-tunnel tests of a manned three-quarter scale model before the German government canceled the program in 1987. Though there is no evidence tying the US to that decision, German sources say the US Air Force was amazed -- and not a little rattled -- to discover that Lampyridae utilized the same radar-scattering "faceting" technique employed by the then top-secret F-117 Stealth Fighter. Unlike the F-117, Lampyridae was designed to go supersonic. It was this aspect, some German engineers believe, that led to a concerned Reagan administration exerting pressure on Bonn to ax the program.