British engineers have unveiled plans for a hypersonic jet which could fly from Europe to Australia in less than five hours.

The A2 aircraft, designed by engineering company Reaction Engines based in Oxfordshire, southern England, could carry 300 passengers at a top speed of almost 6,400 kilometers an hour, five times the speed of sound.

The LAPCAT (Long-Term Advanced Propulsion Concepts and Technologies) project, backed by the European Space Agency, could see the aircraft flying within 25 years, the firm's boss Alan Bond told The Guardian newspaper.

"The A2 is designed to leave Brussels International Airport, fly quietly and subsonically out into the north Atlantic at mach 0.9 before reaching mach 5 across the North Pole and heading over the Pacific to Australia," he said.

The plane, which at 143 meters long would be about twice the size of the biggest current jets, could fly non-stop for up to 20,000 kilometers.

It operates on liquid hydrogen, which is more ecologically friendly as it gives off water and nitrous oxide instead of carbon emissions.