I'm not sure I'd put too much stock (so to speak) in the share price of ATAHQ.PK given that those shares will probably be cancelled as part of the bankruptcy reorganization. I'm actually shocked that they spiked up to nearly $3 when it was announced that Southwest had won the bid, but I suspect that the reminders issued by the company of the ultimate value of the shares brought them back down.
Just to throw some additional info into the ring, ATA currently flies large jets non-stop domestically from MDW to BOS, CLT, DFW, DEN, FLL, RSW, LAS, LAX, MIA, MSP, LGA, EWR, MCO, PHL, PHX, PIT, SFO, SJU, SRQ, SEA, PIE, and DCA. They've already announced that CLT and MIA are closing, and it's unlikely that they'll duplicate WN's service to FLL (5 daily), LAS (10 daily), LAX (6 daily), MCO (7 daily), PHL (5 daily), or SEA (3 daily). Southwest also will have 6 dailies to TPA, so I think PIE (and maybe SRQ) is out. That leaves BOS, DFW, DEN, RSW, MSP, LGA, EWR, PIT, SJU, and DCA -- and if you exclude SJU, that gives you nine cities.
It will certainly be fascinating to see exactly how all this plays out -- and this could certainly cause some disruption to legacy carrier pricing in the SWA/ATA codeshare cities.