Is this the US Air Force’s secret 4,600mph spy plane? Prison Planet.com Posted on January 11, 2018 Posted in Aggregated No Comments Tagged with Sci Tech Daily Mail | The US Air Force is understood to be developing a spy plane that travels at more than 4,600mph (7,400km/h). Share this:Share Share on Facebook (Opens in new window) Facebook Share on Reddit (Opens in new window) Reddit Share on X (Opens in new window) X Share on LinkedIn (Opens in new window) LinkedIn Email a link to a friend (Opens in new window) Email