IT MUST have made a terrific din. But luckily as the aircraft tore across the spring sky over Woomera, South Australia, last month at more than twice the speed of sound, there was no one around to hear it except a few kangaroos. Shot into the sky on the back of a rocket, the plane was testing a new wing design for what might become the next supersonic passenger airliner, known as the "son of Concorde".

The Japan Aerospace Exploration Agency (JAXA), which built the prototype, hopes the next generation of supersonic jets will be carrying passengers within 15 years. The aim is to build a 300-passenger aircraft that could whip you from London to Tokyo in a little over 4 hours.

And the JAXA project, which is coordinated by the Society of Japanese Aerospace Companies (SJAC) and the French aerospace industries association, is by no means the only one. ...