A test flight of the 'world's fastest plane' has ended in disaster after the vehicle crashed into the Pacific Ocean.

The US military's Falcon HTV-2 - which travels 22 times faster than a commercial airliner - was launched amid promises of flights from London to Sydney in less than an hour.

Attached to the back of a rocket, the plane blasted off from Vandenberg Air Force Base in California, before detaching at the edge of space.

But after around nine minutes, the craft stopped sending signals and is believed to have plunged into the ocean.

Engineers had hoped to guide the plane on a hypersonic flight, and that it would reach speeds of around 13,000mph upon its return to Earth.

Travelling at about 20 times the speed of sound and withstanding temperatures of 2,000C, the plane was designed as part of a research project.

A previous launch attempt was abandoned and plane designs changed in April due to a fault on board the aircraft.

Nine minutes into that previous mission, at which point the plane had flown for 139 seconds reaching 16,700mph, an onboard computer detected an anomaly and ordered the plane to ditch in the ocean for safety reasons.

A second attempt on Wednesday was delayed to Thursday because of poor weather conditions.