I suspect the reason we do not see mainstream super-sonic airliners is we simply don't have the technology to make them cost-effective. The Concorde is still a novelty after all these years, probably because its expensive to fly. But my question to all if you is, could we someday, in the near future, see economically feasible super-sonic RJs? After you stop laughing, please give it a hard second thought. I bet it'll happen long before financially practical full-size SSTs. If you think it could happen; how many years away is it? Any thoughts?