What was on Mike Folse’s drawing board at Bell Helicopter that day in March 1965 was supposed to be a hovercraft. It wasn’t. “I had an idea instead,” he explains. “My boss would be on vacation for two weeks.”

Gloom pervaded Bell’s Preliminary Design Group. In a Pentagon competition to develop an ambitious concept for an attack helicopter, Bell’s proposal had just lost out to Lockheed’s—a demoralizing beat-down from an airplane company that had never made a helicopter. At Bell’s Hurst, Texas plant, an exodus was under way as dispirited engineers and executives started burning up accrued vacation time. On his way out the door, Folse’s boss issued explicit instructions: “Forget what you’re working on. While I’m gone, start on a hovercraft.”