Save 15% off your fall Southwest Airlines travel with this coupon by Grant Martin Apr 18th 2008 @ 8:00PM If you have the foresight to have your fall travel already planned, Southwest Airlines just released a coupon code that will get you 15% off between August 23rd and October 30th. Use coupon code DING15 to get your discount, but hurry -- the coupon code is only valid through April 21. Much of Labor day is also blacked out, so if you want to travel over that weekend make sure you take a couple of extra days off and be flexible. Still not good enough? Keep your ears tuned to Gadling. I hear we might have some tickets to give away in the next few weeks.