military
Lockheed's SR-72 Hypersonic Successor To The Blackbird Still Hasn't Flown & Here's Why
https://simpleflying.com/lockheed-sr-72-hypersonic-succesor-blackbird-still-hasnt-flown-why/
The SR-72 emerged in 2013, only to go dark and be classified again; now it is difficult to say if it has been canceled or is in service.