The United States has long led the world in fielding advanced new airpower technologies, from the first-ever miitary aircraft to the invention of modern stealth. But for every paradigm-shifting aircraft like the F-117 Nighthawk, B-2 Spirit or F-22 Raptor, there’s a long list of prototypes, technology demonstrators and design proposals that never see the light of day. These classified aircraft programs serve as proof that America is keeping some of the most exotic flying platforms this world has ever seen tucked away behind the veil of classified funding… And that invariably leaves room for people to let their imaginations to run wild. So, let’s talk about some of the most famous (and controversial) secret aircraft the US has been alleged to operate.