AirTran & Southwest have connected networks.
Southwest® Sale Terms and Conditions:
Purchase by April. 7, 2014, 11:59 p.m. for the respective time zone of the originating city. Travel June 10 through August 20, 2014. Travel valid only on Tuesdays & Wednesdays.
Some flights operated by AirTran® Airways. Displayed prices include all U.S. and international government taxes and fees. Fares not available to/from Islip/Long Island, NY; Providence, RI; and Manchester, NH. Seats are limited.
Fares may vary by destination, flight, and day of week and won't be available on some flights that operate during very busy travel times and holiday periods. Fares are available for one-way travel.
For more info check HERE