Forget the Spruce Goose; the Stratolauncher is set to become the world’s largest airplane when it begins flight-testing early next year. Currently under construction inside a massive, 103,257-square-foot hangar at the Mojave Air and Space Port in California, the carrier plane will be equipped with twin fuselages built from light-but-strong composite materials that will extend 238 feet from nose to tail when complete. Its sweeping wingspan will measure 385-feet—wide enough that if the plane was taxied to the ce…