Kelly Johnson’s SR-71 was conceived during the 1950s as a stealthy reconnaissance ship that would fly too high and fast for enemy missiles to reach. Though limited to about 2,000 knots by aerodynamic heating, the SR-71’s speed has never been surpassed by any manned jet. Its fuselage chines, conceived as stealth aids, became an important aerodynamic feature of many later aircraft. Lightly built of titanium and stainless steel, the Blackbird was leaky, not very maneuverable, and given to cantankerous engine behavior, but it remains possibly the most fantastic-looking — and to many eyes the most beautiful —