I think the sonic cruiser will rise or fall on the fuel consumption issue. Boeing says it won't use more fuel than current Mach 0.8x aircraft. If true, that presumes more fuel-efficient engines. Given such engines, they could equally be used to REDUCE fuel consumption of Mach 0.8x aircraft, so comparing it with today's jets is apples and oranges (though it may be an effective PR ploy for those who don't see through it). The point it that it would use more fuel than an otherwise comparable Mach 0.8x aircraft of the same era. That being the case, it would be more expensive to operate than other planes the airlines could buy at the same time to replace their current fleet - which Airbus is sure to point out!

I personally would not pay a premium to save, at best, 10 percent of door-to-door travel time on a 4000-mile trip. If Boeing builds it, and someone buys it, and they fly it where I'm going, and the price is no higher, and I'm still alive by the time all that happens, I'll be on board. But on balance I think it's a bad idea.