When Concorde was decommissioned in 2003, supersonic air travel became a thing of the past. But work has begun on a passenger aircraft that could go further and faster - flying from Europe to Australia in four hours. Will it ever become a reality?

The European Space Agency's goal is to create a hypersonic passenger plane, one that flies more than five times faster than the speed of sound and six times faster than a standard airliner.

It's not the first time hypersonic flight has been attempted. In 1960, tests took place on the X-15 - half plane, half missile - which carried one pilot and flew for 90 seconds before its rocket fuel burnt out.

Its creators thought it would herald a new era of high-speed civil aviation but more than 50 years later, a hypersonic passenger plane has yet to be tested or even built.