U.S. Unveils Plans for World's Fastest Spy Plane

The SR-72 unmanned plane flies at six times the speed of sound — about 4,200 miles per hour, 70 miles per minute. However, this plane is not designed for travel, but as a military assault weapon, one that would leave enemies with no time to hide.

Equipped with hypersonic missiles, this futuristic U.SAir Force craft designed by Lockheed Martin could strike targets across any continent in less than an hour, according to a fact sheet the company provided to Mashable. But for now it remains a vision, not meant to fly until 2030.

To reach such speeds, Lockheed Martin and Aerojet Rocketdyne, the companies said to be actively developing the plane, will have to create a new type of engine. Engines found in big commercial airliners can hit speeds up to two-and-a-half times the speed of sound before they're no longer efficient. Other engines keep their efficiency up to four times that speed, but getting to mach six will require a hybrid engine, one that uses a turbine when it's not going too fast, and a supersonic combustion ramjet when it's ready to move. Read more...