DALLAS - The bidding war for bankrupt ATA Airlines' assets heated up on Friday when Southwest Airlines offered at least $100 million in cash and loans for gates at Chicago's Midway Airport and an alliance with ATA, its main rival there. Southwest chief executive Gary Kelly said the bid represented the only way that his company could meet its top goal of expanding in Chicago. He said Southwest's proposal would let ATA Airlines Inc. still operate at Midway but with fewer gates. Southwest is seeking to upset the bid of another low-cost carrier, AirTran Airways, a unit of Orlando-based AirTran...