NO Blackbirds are currently flying. NASA did have a couple, but they haven't flown since 1997 when the X-33 program was cancelled and have also become museum displays (one at Edwards and one at KSC apparently). They are not being operated since NASA didn't get the windfall of customers it was expecting for the aircraft to be used as hypersonic and space instrument test platforms. The last USAF
operations involving the SR
-71 were also in 1997 when lack of support killed the attempted revival of USAF
Blackbird operations after only a few training flights.
The CORRECT chronology for the Blackbird development was A-12, YF
-12 then SR
-71 (M-21/D-21 being a development from the A-12 project also). The A-12 was the design built for the CIA
and it was a single person direct overflight aircraft. The SR
-71 in a sense actually was developed more as a direct benefactor to the A-12 while the YF
-12 Interceptor was more of a parallel program. The SR
-71 is different from the A-12 in that it is a two person aircraft with the back seater running the recon equipment and it isn't intended to do just direct overflights, but can take recon runs off the coast of a threat nation while cruising along at Mach 3 (although it can and has made direct overflights as needed). The SR
-71 is also a USAF
project instead of a CIA
As for the size of the plane, it is big in terms of it being a two seater, but it isn't as big as one might think. It is bigger then an F-14 or F-15, but compared to a plane like a KC
-135 or a B-1, it looks rather small.