4 Answers

other reports say mach 14 , highly unlikely

Mach 3.5

the speed record was 2,236 actualy mph and mach 3.4    

so around 2000 mph    3 mach

Check in Jaynes latest Military Aircraft guide the jet, holds the *official speed record of 2,193 mph, *about Mach 3.3.  And although officially retired from federal service, early 1990, the SR-71 Blackbird, *would be a slow-poke compared to the Mach 8 aircraft (5,280 mph) seen today. How about that for a zinger?  

However, seemingly still classified is the Blackbird's flight range and her true flight ceiling.  (Pardon my spelling please? It be a bit late.)

*That comes from here:  *Mach 8 Aircraft at:  j_kidd.tripod.com/b/126.html - (NOT A LINK)

I hope gets a bit more specific answer for your question.

Heavy Doc