An American company is developing an unmanned aircraft capable of travelling at six times the speed of sound.

The SR-72 supersonic plane would use a turbine-ramjet engine to reach 3,600 MPH, said Lockheed Martin.

The company said the plane will be designed for high-altitude surveillance, but could also be armed with guns or missiles.

Just don't look to the skies yet - the plane isn't scheduled to be operational until 2030 at the earliest.

The jet is designed as the successor to the Blackbird SR-71 spy plane, which first flew almost 50 years ago in 1964 but was able to reach Mach 3 (1,800MPH).