Hello everyone,

I keep reading both here and on Airliners.net that in deciding where to put their hubs that airlines must look at O&D and not just geography -- that is to say, that AA's hub at ORD is profitable both because of it's "mid" location and b/c it's a huge O&D market, for example, where as CO's CLE or DL's CVG aren't as much.

So my question is: why is this true? What is it about O&D traffic that is so lucrative for airlines?