If CLT survives as a hub it will buck the trend of small-market hubs disappearing - MEM, CVG, PIT. CLT has very very low O & D, ala RDU & BNA. "Most profitable" hub, maybe in terms of margin due to very low costs certainly not in raw $$ amounts. "7th busiest airport" Fresno could be the 7th busiest airport if you decide to funnel all your connections through it.