The American X-51A Waverider was designed to reach Mach 6, or 3,600mph, after being dropped by a B-52 bomber off the southern California coast last Tuesday. (Aug:14th)

It is was an unmanned plane with an exotic scramjet engine,
that failed to reach its top speed as its engine shut down prematurely, some ten seconds after being released from the
B-52 bomber.

The Pentagon has been testing hypersonic technologies in hopes of delivering strikes around the globe within minutes.