[justin66]

You can see how certain people would think the SR-71 would naturally be a permanent replacement for the U-2. It'll fly at the same extreme height a lot faster, etc. etc. If you're not aware of the enormous operational cost, which is what really killed the blackbird, it seems obvious which one should succeed. (or if it's not your money...)

Every time one of these threads comes up I think I should reread Ben Rich's book, which I read over twenty years ago and gave to a friend about five years ago. It would be interesting to recall his perspective on this. I think he had something in there about how proud they were about keeping the costs of the reactivation and final flights of the SR-71, which were sort of mandated by congress, as low as possible. They were still a lot more expensive than, for example, recent programs to equip the U-2 fleet with more modern avionics.