Aircraft Speed Altitude Mach Number
SR-71 Blackbird 2,275 mph
(3,660 km/h) 80,000 ft
(24,385 m) Mach 3.35
MiG-25 2,110 mph
(3,390 km/h) 42,650 ft
(13,000 m) Mach 3.2


This data is from Aerospaceweb. Question: SR-71 looks like alien plane, have
very special design (incl tanks what start to keep fuel on flight only)etc
etc. Mig-25 looks as pretty usual plane. But difference in speeds is
relative minor, expecially if to look at what altitude it is reached. How it
is possible? Do anybody have more data? Say, about SR-71 performance at 40
000 feet?