The master lease agreements that apply to airlines at Hartsfield-Jackson Atlanta International Airport do not expire until September 2010, but talks between the sides have already heated up.

Atlanta-based Delta Air Lines Inc., the world's biggest carrier, and discount carrier AirTran Airways, a unit of Orlando, Fla.-based AirTran Holdings Inc., say that if their costs are too high they may be forced to move some connecting flights to other airports.