The first supersonic manned flights occurred in the years immediately following the Second World War. The first that was officially recognised and recorded took place during 1955. By 1962 the technology had reached the stage where the use of supersonic aircraft for passenger transportation had become a serious possibility. A joint announcement was made by the British and French authorities that they would co-operate in the development of a new supersonic aircraft designed for commercial passenger transportation. There soon followed similar announcements of American and Soviet projects to develop fleets of supersonic passenger airliners. Almost from the very start, these programmes ran into difficulties with design problems and cost overruns. As the programmes slowly got underway, and public awareness of the issues increased, two sets of environmental concerns came to the fore.

The more obvious and more spectacular issue was the problem of the shock wave or ‘sonic boom’ that is always associated with an object moving through the air at supersonic speeds. This produces an effect like a loud thunderclap on the ground when the aeroplane passes over, and under certain circumstances it could crack windows or knock small ornaments or crockery from shelves. It soon became apparent that aircraft would have to maintain sub-sonic speeds when travelling over populated land areas. Even so, a series of concerns were strongly expressed in various forums.