The SR-71(blackbird) was scrapped in 1998. Why? The military wouldn't scrap a successful design without having something better in the wings. The article tries to explain.
https://www.yahoo.com/news/rumors-secret-warplanes-preceded-mach-111600240.html
gramps
https://www.yahoo.com/news/rumors-secret-warplanes-preceded-mach-111600240.html
gramps