To date, only a few aircraft in the world have been able to overcome the speed of Mach 3. The undoubted "pioneer" of this direction is the A-12 "Oxcart", which became the predecessor of the secret American reconnaissance aircraft SR-71 Blackbird. The A-12 made its first record flight back in 1963, exceeding the sound barrier three times at an altitude of 27, 400 meters.
Lockheed Skunkworks developed the A-12 for high-altitude strategic reconnaissance, at that time the aircraft was considered inaccessible to air defense systems. Compared to the SR-71 Blackbird, it was somewhat shorter, lighter and even faster. The main advantage of the SR-71 is its long flight range, which, as a result, determined their further fate: the A-12 was decommissioned in 1968, and its competitor flew until 1999.
One of its participants, Thornton Barnes, spoke about participation in the A-12 development project in his book "My Odyssey to Area 51". Over a long career, he has worked for the CIA, NSA and NASA. As an expert in hypersonic flight, he was included in the key development team. Prior to that, he was engaged in special projects for the study of Soviet combat aircraft, the creation of drones and stealth aircraft.
And recently, Barnes published declassified images of tests of a full-size wooden mock-up of the A-12 at Area 51. The strangest part of them is that the plane is upside down on them.