Coupon sites such as RetailMeNot provide coupons for Southwest Airlines, as of 2015. The Southwest website also provides various special offers and promotions on the Special Offers page.
The Southwest website's Special Offers page includes discounts on flights that are purchased during certain seasons or times of the year.
RetailMeNot provides a variety of different coupon codes to be used by people booking their flights online. There are coupon codes to get a bag checked for free, as well as a discount when purchasing a business class seat instead of economy seat. There are also free drink coupons when purchasing certain types of seats with Southwest.