Issues that need to be overcome:
Sonic boom. I believe some progress has been made in minimising sonic booms, but it’s still a big problem overflying land. Partially why LHR-NY is one of only a few viable routes as it’s water most of the way
Noise. Anyone remember Concorde? Now sub-sonic aircraft are so much quieter than in the Concorde days, I very much doubt anyone would put up with Concorde
Drag is very non-linear. From my university days I remember a graph (but can’t find it now) showing that drag vs speed had a bit of a dip around M2.2, not un-coincidentally around Concorde’s speed. After that it goes up, and fast.
Fuel usage/cost. Concorde was ~4x subsonic. Given we’ve seen oil gyrate from 110 to 25 and back up to 80ish, who would take the risk of producing a white elephant should oil reach maybe 110 again?
There are very few city pairs that warrant it. You can’t overfly land super-sonic and you wouldn’t want to go for much more than 3 hours as Concorde seating was economy class width and pitch. Modern private jets fly fast enough, and you can work on a plane, it’s not dead time. When people in my office flew Concorde it was only because they needed to do meetings the same day in London and NY, not because it was quicker. The time difference and highish latitudes help here. Are there any other city pairs that work??
Every 2-3 years we get a new press release saying its imminent. I don’t think this time it’s different.
Fix all the above and it’ll work
Very interested to hear more up-to-date developments on any of these issues…