I've previously written a few relevant comments that hopefully answer in parts: [1] https://news.ycombinator.com/item?id=27386119 https://news.ycombinator.com/

I've previously written a few relevant comments that hopefully answer in parts: [1] https://news.ycombinator.com/item?id=27386119 https://news.ycombinator.com/item?id=27386119 [2] https://news.ycombinator.com/item?id=35124271 https://news.ycombinator.com/item?id=35124271 [3] https://news.ycombinator.com/item?id=35126733 https://news.ycombinator.com/item?id=35126733 Relative to say Concorde, acquisition costs and direct operating costs need to decrease and # of revenue-generating flights/time need to increase for viability. All of these point to slower speeds. If the perceived boom noise of the "quiet" supersonic designs is low enough, supersonic overland flight could potentially be permitted (NASA is trying to make this possible via this X-plane), with vastly more addressible market. Low boom limits the Mach number.