Supersonic has also been dead because passenger supersonic flight is banned over the continental US (and probably similar restrictions exist in Europe). In the

Supersonic has also been dead because passenger supersonic flight is banned over the continental US (and probably similar restrictions exist in Europe). In the US the regulations will be getting reviewed depending on the results of studies on building supersonic jets that make less noise (after which it'd be down to if they can be made efficient enough to be profitable).