WHEN a British Airways Concorde travelling from New York touched down at Heathrow airport, in London, on October 24th 2003, supersonic passenger travel came to an end. Concorde was a technological marvel, but never a commercial success. Only 14 of them entered service. Yet the idea of building a successor has never quite gone away. Aircraft-makers review the idea from time to time. A number of groups are working on small executive jets intended to travel faster than the speed of sound. The trouble is, something else has also refused to go away: the shock wave known as a sonic boom that emanates from a supersonic aircraft.
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