Imagine taking off from any airport and landing anywhere in the world in less than two hours. Or making a quick trip to space and back. Sounds like science fiction? Not any more. Technology now being developed by NASA could achieve such rapid travel times within two decades, giving limitless possibilities for international travel and access to space. Over the next five years, NASA is spending over $700 millions to develop so-called 'hypersonic' aircraft which can fly over 30 km above the Earth's surface at cruising speeds in excess of Mach 5, or 6,000 kilometres an hour. The primary goal of the research project - called 'Hyper-X', is to revolutionise the way we reach space; but NASA also believes it will replace everyday air travel between continents. Unlike conventional jet planes or rockets, the Hyper-X planes will be powered by a combination of air-breathing rocket or turbojets and ramjets. Air-breathing engines achieve their efficiency gains over rocket systems by getting their oxygen for combustion from the atmosphere, as opposed to a rocket which must carry its own oxygen. These systems capture air from the atmosphere during flight ‹ an arrangement that improves efficiency up to 5-10 times greater than that of conventional chemical rockets. Once a hypersonic vehicle has accelerated to more than twice the speed of sound, the turbine or rockets are turned off, and the engine relies solely on oxygen in the atmosphere to burn fuel. The commercial airliner version will level off and cruise at three times the altitude of today's planes. The spaceplane version, however, will continue to climb, accelerating all the time. When the vehicle reaches more than 15 times the speed of sound, the engine converts to a conventional rocket-powered system to propel the craft into orbit. NASA believes the Hyper-X planes will lead to practical aircraft before the middle of the century: a fleet of commercial hypersonic vehicles, travelling between dozens or even hundreds of 'sky ports' around the world - and beyond it.