I commute from Miami to Atlanta and if there weren't 20+ flights a day I would be royally f$&@3d. Haven't tried Atlanta to Chicago. Depends on what regional you fly for. Skywest has a few flights on that route so if you work for them or Expressjet you would have priority on own metal. You do not want to commute from IAD to ATL. Or ATL to any other delta hub. Any other airline other than delta to/from Atlanta is pretty commutable. For example, if you get on a flight from Atlanta to Miami on an American flight, it's usally only half full, while a delta flight is oversold by 10 with 50 standbys.