for reasons I discussed here. Blazing speed isn't as useful for reconnaissance as many people believe.
There is some reasonable speculation that a super high speed plane was built and tested in the early 1990s, with perhaps the most credible evidence being the sesmic measurements of sonic booms crossing the California coast back then. There's little evidence that it exists anymore, and not much reason for it. For that matter, I've never seen even remotely credible Aurora reports that mentioned Mach 10 speeds. Most of the Aurora speculation was for a Mach 5-6 vehicle.
Sonic booms are detectable by seismographs, making it a lot harder to hide supersonic vehicles from the public for long. For example, the Blackbird was developed in secret back in the early 1960s, but when it came time to conduct more realistic testing, LBJ unvealed it to the public.
Space/Science » in reply to About that X-43 being the 'first' air-breather to reach Mach-10.
I'm skeptical that Aurora exists...