Zeke
While I agree with most of your comments, I find it hard to believe that the Sonic Cruiser was just a marketing exercise.
On most heavily used international routes, slots are congested and there some slots are more valuable than others.
Obviously any airline is going to place its first SCs in the primetime slots. So they replace a 747 with a 250-seat SC, which will be mostly premium class plus fullfare eco. Either they give the surplus economy pax to the competition or they need a bigger plane to fly them off-peak.
Bigger plane = A380.
So the launching of the SC after the A380 inevitably supported the latter's sales among those airlines that face this trade-off.
What I have trouble believing is that Boeing would have risked supporting the A380's sales if they didn't think the SC was going to fly.
but I could be persuaded.
answer=42