Two years ago, in a landmark deal, the United States announced it would sell 105 F-35 Lightning II Joint Strike Fighters to Japan. Once completed, it would make Japan the world's No. 2 user of the F-35, second only to the United States. As keen as both Japan and the U.K. are to acquire America's most advanced (and in-production) fighter jet today, it turns out they're even more interested in acquiring something better later on.