Larry and I wrote our responses at the same time. After I finished mine, I saw his and noticed his comment about the SR-71. I said Mach = 3.4 and Larry said Mach = 3.2 . Larry is more correct. I meant to say: Mach = 3.14 . I got my number from an Air Force ground crew guy who did SRs for a living. The SR-71 could probably dash to a slightly higher Mach number but it would sustain permanent damage as a result. SR-71s don't fly anymore which is a real shame. The SR-71 was one of the "coolest" things that ever flew. IMHO, Kelly Johnson walked on water.

Gary