Flying from London to Sydney in 2.5 hours may be possible, according to Virgin Galactic.

Speaking at the Wired 2013 conference, the company's commercial director Stephen Attenborough said the flight could be possible by travelling above the atmosphere, using gravitational pull to travel at faster speeds.

This could achieve potential speeds of approximately 4,200 mph.

Mr Attenborough said: "If we can get this first step right - take people into space and keep them safe in commercially viable aircraft - the aim [is] to try and push long-haul aviation above the fragile atmosphere into space."

Virgin Galactic's Space Ship 2 (SS2) aircraft has only reached the edge of the stratosphere - the second lowest section in the planet's atmosphere - although the company is still positive for next year's maiden flight.

SS2 is initially flown up by a carrier aircraft called White Knight before being released and flying itself higher.

It has already received $80 million (£50 million) in deposits from 640 people interested in being the first on the service into space.