Actually, they do not capacity control. They do have blackout dates, but that's it. To quote from their website: "Rapid Rewards is the only major frequent flyer program that doesn't limit the number of seats available for use with your roundtrip Award. If a seat is available on the flight you want to take, it's yours! Best of all, Southwest Airlines has limited blackout dates so there are virtually no limitations on when you can use your roundtrip Award - imagine the possibilities! "