On 17 June 1943, Lockheed Aircraft designer Clarence L. “Kelly” Johnson received the official go-ahead from the US Army Air Forces to begin development of the XP-80 prototype, which led to America’s first operational jet fighter. The XP-80 was completed in total secrecy by a team of 130 people and delivered in just 143 days, under budget and ahead of schedule. That aircraft was the first of many advanced development programs designed and built by what today is known as the Skunk Works. Following a disciplined set of guiding principles known as Kelly’s Rules, the Skunk Works has produced such revolutionary aircraft as the U-2, SR-71, and F-117 as well as the XF-104, YF-22, and X-35 prototypes.