Originally, AirTran airways had a promotion where you would receive double credits on every flight you take through May 15th. Similar to the Southwest promotion, AirTran has also decided to extend this promotion to June 12, 2013. Typically, you earn 1 credit for every one-way flight in coach and 1.5 credits for every one-way flight in business class. During this promotional time period you will instead earn 2 credits for every one-way flight in coach and 3 credits for every one-way flight in business. To redeem for a free roundtrip ticket it requires 16 credits, so if you fly 4 roundtrips during this promotion period a free ticket is yours (for coach travel)!
If you have already registered for the promotion you will automatically be registered for the extension of the promotion. If you have not yet registered, you will need to register here.
Now, the one major caveat to this (which I HATE and Southwest Airlines does the same thing) is that you must have registered for this promotion prior to booking your travel.
Also, since some Southwest and AirTran flights are being operated by each other, regardless of which website you book through, this promotion is only valid for those flights booked through AirTran, not Southwest. For flights booked through the Southwest site you’ll earn double Southwest points by registering through their promotion.
Also remember, even if you are not a big AirTran traveler you can transfer your credits to Southwest if that is preferable.