but I have my doubts. There were some mysterious photos published in Aviation Week & Space Technology magazine back in the early 1990s of mysterious contrails that didn't match any known plane. They appeared as pearls on a string, like a pulsejet engine would produce. There have been no published photos by a credible source since.

It's possible that something along the lines of Aurora was tested but not fielded. Even the blackest military planes are typically unveiled or at least acknowledged in less than 10 years after they were first flown. This covers the U-2, Blackbird, F-117A, B-2, and several stealth prototypes. Extreme secrecy makes operational testing and training very difficult and expensive. If you can't conduct realistic testing and training, then the plane is useless as a weapons system.

And for Lee, extreme speed isn't all its cracked up to be in terms of military utility. The Blackbird was extremely fast (Mach 3.15 cruise according to a coworker of mine who was a backseater on them from 1985-1990) and that was more than fast enough to do the job. Going faster in and of itself doesn't make the plane more useful or capable. In today's environment, stealth is more important than raw speed.