Southwest is offer a 15% discount on tickets purchased by April 21 for travel through October 30 using promo code DING15.
The terms and conditions aren’t onerous. Discount applies to roundtrip tickets booked at Southwest.com. August 29, 2008 through September 1, 2008 are blacked out for travel with this discount. The discount doesn’t apply to Business Select, Business, or Senior Fares, and doesn’t take money off of taxes.