What You Need to Know: The YF-12 was a high-speed interceptor developed ... Now, with no Mach 3 interceptors in development, Lockheed’s famed designer Kelly Johnson proposed a variant of their ...

The Lockheed design was selected over Convair's FISH and Kingfish designs, and it served as the precursor to the United States Air Force YF-12 prototype interceptor and SR-71 Blackbird.