The race for the next supersonic flight is on. I've mentioned the QSST concept before now here comes the A2 airplane which takes things a step further It is a hypersonic plane designed by Reaction Engines in England. The A2 is designed to carry 300 passengers at a top speed of 4,000mph and will run on a liquid hydrogen engine. The A2 will be twice the size of the biggest current jumbo jets and could fly between Europe and Australia in less than five hours. Don't look for this one anytime soon, the company has said that the aircraft could be operating within 25 years.