The A2 would be twice the size of the biggest current jumbo jets

The A2 aeroplane, designed by Reaction Engines in Oxfordshire, would carry 300 passengers at a top speed of 4,000mph.

The company said the aircraft, which is still at the concept stage, could be operating within 25 years.

It said the A2 would be able to keep a sustained speed of 3,800mph, more than twice the speed of Concorde.

At 143m (156yds) long, the A2 is roughly twice the size of the biggest current jumbo jets.

It would run on a liquid hydrogen engine being developed by Reaction Engines, based at Culham near Abingdon.

The first man-made object to reach hypersonic speeds was the two-stage US "Bumper" rocket, assembled from a captured German V-2 rocket in 1949.

Astronauts and cosmonauts have all reached hypersonic speeds while passing through the atmosphere on their way to and from orbit.

Current research, however, focuses on sustained hypersonic manned flight within the Earth's atmosphere, which has not yet been achieved.