Once upon a time, Lockheed Martin (NYSE: LMT) built the most expensive fighter jet in the world, the F-22 Raptor. Stealthy, fast, ultra-maneuverable, and equipped with advanced sensor systems, the fifth-generation F-22 was considered the world's best fighter jet when introduced in 2005. After years of hemming and hawing, the U.S. Air Force has decided to proceed with the development of a new best-in-the-world fighter jet -- the Next Generation Air Dominance fighter (NGAD) -- to replace the F-22.