In the summer of 1942, 10 months after they started, the engineers loaded the first pair of working jet engines, each producing 1,300 pounds of thrust, onto a railcar and shipped them to the Muroc Army Air Field, in California’s Mojave Desert. The aircraft designer Larry Bell was working in parallel with the GE team and building America’s first jet, the XP-59. On Oct. 2, 1942, the plane soared to 6,000 feet, a small first step for a technology that ended up shrinking the world. The engine, called I-A, is now part of the Smithsonian collection in Washington, D.C.