US Airways has hubs in CHarlotte, Pittsburgh, Philadelphia, and BWI (plus I think Dulles as the Metrojet hub). Delta also has a mini-hub in Orlando for Comair and Delta Express.

As for airports I am familiar with, Chattanooga has four: DL to Atlanta and Cincy, NW to Memphis, UA to Chicago, and US to Charlotte (although only US flies here itself instead of using a commuter line--and half of theirs are really Piedmont). Nashville has:

American to DFW, O'Hare, LaGuardia, Raleigh, and LAX
Continental to all three hubs
Delta to Atlanta, Cincy, Little Rock, Louisville, Orlando, and DFW (also to, but not from, SFO)
Northwest to all three hubs
United to Chicago, Denver, and Dulles
USAirways to Charlotte, Indy, Little Rock, Philly, Pittsburgh, and National

Southwest to Austin, Baltimore, Birmingham, Midway, Cleveland, CMH, Fort Lauderdale, Hobby, Jax, KC, Vegas, Islip, LAX, ManchesterNH, New Orleans, Oakland, Orlando, Phoenix, Providence, San Antonio, San Diego, Seattle, and Tampa
AirTran to Gulfport, MS
TWA to St. Louis
Corporate Express to Atlanta
Skyway to Milwaukee

Air Canada to Toronto

[This message has been edited by silverpie (edited 05-11-99).]