If you read the development story for the SR-71, that thing was not so much developed as invented from the ground up. It was made out of titanium, pioneered stealth technology, radiated heat, had insane engines that almost acted like ramjets, used unique, specially developed fuel and was so fast that nobody really knew what its top speed was, because nobody had tried it. If somebody fired a missile at it, the countermeasure was to just go faster as by the time the missile reached where you had been, you'd be long gone. It remains one of the most remarkable things ever invented. It still boggles my mind thinking about it.