Airtran is an airline with its corporate hq. in Orlando, but is based mainly out of Atlanta. They are a low-fare carrier like Southwest Airlines. They fly older DC-9's which used to belong to Valujet (with whom they merged) and brand new Boeing 717's which they are purchasing and phasing in to replace the fuel-guzzling DC-9's. They used to have a couple boeing 737's also which belonged to Airtran before the merger.
I have flown them once (on a DC-9) and was happy with the flight. The biggest plus they offer, is any city which they serve ends up having lower fares overall (just like cities served by Southwest airlines.) However, if people do not fly them and support them, they will pull out and start service to another city (like they did in Des Moines, IA. - pulled out a couple years ago and now serve Minneapolis/St. Paul instead.) Fares then went up in Des Moines as competition was eliminated.
They also do not offer meal service (same as Southwest). They do, however have pre-assigned seating like all other major airlines (except Southwest).