30% Off Southwest Flights? What To Know About The Airline's Latest Sale

Southwest Airlines to end its free checked bag policy

The new policy will affect tickets purchased on or after May 28.

• Southwest Airlines is offering 30% off select summer and fall flights booked by Thursday night.
• The SUMMER30 promo code applies to Wanna Get Away and Wanna Get Away Plus fares for various travel dates and routes.
• The discount has limited availability and restrictions depending on the days of the week and specific routes.

Southwest Airlines is offering 30% off many summer and fall flights, but you have to book by 11:59 p.m. PT on Thursday to get the deals.

Using the code SUMMER30, Southwest passengers booking new tickets can get up to 30% off the base fare on Wanna Get Away and Wanna Get Away Plus fares on many travel dates.

Still, as with most airline sales, it's important to read the fine print, because there are some limits to a carrier's generosity.

Generally, the sale applies to flights operating:

• Between May 20 and Oct. 2 for flights in the continental U.S.
• Between Aug. 17 and Oct. 3, for flights between the continental U.S. and origin or destination airports abroad or in Hawaii and Puerto Rico; and
• Between May 20 and July 2 for Hawaii interisland flights

But the deals won't be available on all flights.

According to the airline, the promotion is only valid on flights operating from the continental U.S. to Hawaii and international destinations on Sundays, Mondays, Tuesdays and Wednesdays.

On flights from Hawaii and international origins to the continental U.S., the deal is only valid on flights operating on Tuesdays, Wednesdays, Thursdays and Fridays.

For interisland Hawaii flights, the deal is valid only on Tuesdays and Wednesdays.

For travel to and from San Juan, Puerto Rico, the deal is valid on Mondays, Tuesdays, Wednesdays and Thursdays.

Beyond those broad restrictions, the deal may have further limited availability.

"Seats, days, and markets are limited," the fine print says. "Discount availability may vary by destination, flight, and day of the week and won’t be available on some flights that operate during very busy travel times and holiday periods."

To check if your flight is eligible, enter the promo code before starting your flight search.

"If you have entered the promotion code SUMMER30 in the Promo Code box on Southwest.com or swabiz.com during the Booking Period, then while selecting your flights, savings in the base fare will be visible as a strike-through of the original fare on eligible flights," Southwest's website says.

Zach Wichter is a travel reporter and writes the Cruising Altitude column for USA TODAY. He is based in New York and you can reach him at zwichter@usatoday.com.