Volume 2 of The Wind and Beyond begins with a narrative of the genesis of the DC-3. That airplane, grandmotherly today, was as daring a damsel in 1935 as the SR-71 was in 1964 or Concorde in 1976. It incorporated in a single design a number of features that had recently become “shelf items”—that is, proven and available technologies—including a clean, streamlined shape; faired wing roots; smooth all-metal, stressed-skin construction; retractable landing gear; constant-speed propellers; landing flaps; and fully cowled supercharged radial engines. Today, we take all these for granted, but at the time they were, separately as well as collectively, exciting novelties. Each of these features provided not merely measurable but large and obvious gains. Together, they produced an airplane that doubled the cruising speed of its predecessors.