SR-71 Blackbird

Kelly Johnson and the Skunk Works designed the SR-71 in the early 1960s to replace the U-2 spy plane. Built largely from titanium (sourced covertly from the Soviet Union), the Blackbird expanded in flight due to thermal heating at Mach 3+. Its engines transitioned from turbojet to ramjet operation at high speed. The aircraft leaked fuel on the ground because panels were designed to seal only when heated in flight. No SR-71 was ever shot down despite thousands of missiles fired at it. The aircraft set records that still stand: 2,193 mph and 85,069 feet. Only 32 were built, each a hand-crafted masterpiece of aerospace engineering.