Actually OOZ662 the SR71 did leak like a seive (sp?) but on the ground. The reason was, that because it flew as fast as it did, it would generate alot of heat on the airframe surfaces. This would cause expansion. In order to not have the airframe buckle at extreme speed due to heat, allowances were made.
If I recall correctly the fueling procedure for these birds was to put enough in to get it airborne and meet up with a tanker. Fuel was topped up in air.
I believe the actual numbers for this aircraft are still to this day classified, however it is generally accepted that it was capable of at least Mach 3 and altitudes in excess of 80,000 ft. (the RCAF has clocked it passing through our airspace at mach 3+).
A remarkable aircraft no doubt, and sorry to see it retire (although, doesn't NASA still have one?).
I think though, that for me, it is definetely one of the "sexiest jets" there is. F-18 is one too...just a damn pretty bird.
Cheers,
RTR