I'm curious to see the fuel efficiency. Wind resistance has to be way way higher at these speeds, but it also appears to be flying at much higher elevation so they may cancel out to a certain degree.
Even if fuel economy was somehow better, it would still lead to more fuel getting burned. Because the super rich only have so much time in their lives to spend in the stratosphere or elsewhere and shorter flight times could noticeably shift their trade-off decision about the inconvenience of flying vs the inconvenience of not being where they'd like to be. Outliers in wealth aren't quite as much outliers in ecological footprint because fortunately there's only so much you can consume, but a supersonic revival would help close that gap.
A part of me sure loves the nostalgic idea of technological bigger-better-faster, but the rest is fully aware that this is not the progress we are looking for. It's bad enough when private investors put money into destructive technology like this, but if it was my tax money, I'd be shouting at them.
