Vello Kala wrote:
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?

Most reports I've read said the Mig-25 could only do over Mach 3 for a
very short period of time, and it destroyed the engines in doing so.

With no comments on its veracity, see, for example:

Mig-25
PERFORMANCE:
Max permitted Mach No. at height: Mach 2.83
Max level speed at 13000 m (42,650 ft): 1,620 knots 3,000 km/h 1,865 mph
at S/L: 647 knots (1200 km/h; 745 mph)
Max cruising speed at height: Mach 2.35
Econ cruising speed: Mach 0.85
Service ceiling: 21,000 m (68,900 ft)

The MiG-25 that was clocked at Mach 3.2 by the Israelis achieved this
speed while running from an intercepting F-4 (which can barely manage
Mach 2 on a good day--before running out of fuel). Upon landing, both
engines in the MiG had to be replaced.

Victor Belenko, the Foxbat pilot who defected in 1976, stated that the
top speed of the MiG-25 was Mach 2.8, but flight above Mach 2.6 was
difficult because of a tendency of the engines to overspeed. Victor
related that MiG-25 pilots were in fact restricted to flying below Mach
2.5 except with special permission.
- http://www.espacetickets.com/foxbat.htm