Southwest Airlines (LUV) is up 0.65% to $12.40 in midday trade, after AirTran Airways (AAI) shareholders approved selling the discount airline to Southwest for $1.4 billion. AAI is unchanged at $7.32 at last check. The deal would give Southwest a foothold in Atlanta and routes to Mexico and the Caribbean in line with the company’s efforts to expand its coverage area. Southwest has to receive approval from federal antitrust regulators before it can close the deal.