DAY and TYS are outstations. You generally fly into a hub at the start of a trip and go from there. You don't fly in and out of an outstation all day long usually.
For example from DAY you might fly to PHL or CLT and then proceed to do hub and spoke stuff from there (EX: CLT to GSP to CLT and then CLT to ORF to PHL and then in and out of PHL with the last leg of the trip going back to your base).