Mach 2+ the fuselage grew over a foot from heat expansion. They were built mostly of Titanaium as as Stainless would melt from high temps of friction of airIt sure does. BYW, the SR71s fuel tanks leaked while it was on the ground. It took the heat / friction of Mark 3 to get them to seal up properly.
Pilots refer to this as a 3 second plane....you had to scan the gauges every 3 seconds and adjust the throttles which also adjusted the engine nose cones.