Note the “string of diamonds” shockwave in the exhaust.
Can you give a clue of what that indicates?
It’s indicative of a pulsed hypersonic shockwave. The rumored Aurora spy plane (or whatever it was) left a very similar contrail that’s been photographed several times. Aviation experts theorized it was the exhaust of a hypersonic scramjet powered aircraft capable of speeds in excess of Mach 5.
You couldn’t see the aircraft, but you could see the “footprints” it left in the sky.
There was one north sea oil worker who described an unusual looking triangular aircraft hanging on the refueling boom as it passed overhead. Sketches but no photographs.