Like Milt, I would add a rider or 2:
Are you talking "regularly achievable" speeds or the sort that overstressed the airframe and that the pilot may or may not have survived?
There are several examples during WW2 of different aircraft types being dived into the ground at high M numbers - both in combat and not - where (it is surmised) the pilot discovered compressibility effects too late to do anything about it.
SD