The North American XB-70 Valkyrie was a prototype nuclear bomber designed for the Strategic Air Command in the late 1950s. Taking flight for the first time in 1964, this six engine behemoth could carry its nuclear payload at speed exceeding mach three. The cost of the aircraft, loss of one of the prototypes in an accident, and the lack of range compared to the B-52 Stratofortress were the undoing of this amazing machine. The only remaining survivor sits in the Museum of the United States Air Force in Dayton, OH. Unfortunately the developers have not made the jet engines adjustable as far as being able to increase or decrease the amount of thrust they produce, so this XB-70 can only flight at a top speed of around 850 mph or so. Still, it's a really incredible plane to fly. A warning to those with older or weak mobile devices: this plane will be laggy on anything but low graphics. Those of you who are blessed with iPads or high-end Android devices shouldn't need to worry about it. As always, good luck and safe flying.