The airline formerly known as ValuJet. It is a budget airline, serving many routes primarily along the east coast of the United States. ValuJet's chronic maintenance problems came to light after a tragic plane crash in the Florida Everglades. After restructuring and the paying of reparations, they changed their name to AirTran Airways and forgot that their entire past existed.
From what people have told me, AirTran is still not a good airline to fly. Although their fares are cheap, and are made even cheaper through their A-Savers Internet fare specials, their service is still very poor. One friend of mine was delayed for nine hours on the ground in Pittsburgh because they had to fly an entirely new plane up from Georgia to get to New York-LaGuardia (a one-hour flight from Pgh). I have seen similar horrendous experiences on message boards, although that's not to say that every flight is necessarily bad. YMMV.