SR71
Well, I suppose it depends on what your definition of glide ratio is for a powered aircraft. Engine(s) windmilling, seized, dropped off...? Generators/hydraulics on/off...? RAT out...?
I prefer to think what it would be if there was no thrust/drag from the engine installation, so you get an idea of what the airframe is capable of. In this respect, I still think modern jets are way ahead of their predecessors.
