[Expired] New Southwest Airlines Promo Offers Flights From $39 [Book by August 21]

Updated: August 22, 2025, 7:12am CDT

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Table of Contents

Southwest Sale Details
Recap on Recent Southwest Changes
Final Thoughts

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Update:

The offer mentioned below has expired and is no longer available.

Southwest Airlines is out with a new promotion with one-way flights starting at just $39 — but only if you book soon, as this promotion ends on August 21.

With this offer, you can travel from September 2025 to March 2026. Whether you’re flying within the U.S. mainland, to Hawaii, or to international destinations, you can score flights for a great price.

Here’s everything you need to know about Southwest’s latest promotion.

Southwest Sale Details

This sale offers fares from $39 one-way on many Southwest flights. You must book by August 21, 2025, at 11:59 p.m. PT. The full terms are on the promotion’s landing page. This sale applies primarily to Basic fares, but Choice fares are included on some routes.

Be aware that the eligible travel dates vary by destination, and the sale only applies to flights booked directly with Southwest. Seats, days, and markets are limited, so make sure to check the full terms and conditions when booking.

However, there are no restrictions on which days of the week you can travel.

Eligible travel dates are as follows:

Continental U.S.
- Travel from September 9, 2025, to March 4, 2026
- Blackout dates: November 21 to 26; November 28 to December 1, December 19 to 23; December 26 to 29, 2025; and January 2 to January 4, 2026
To Hawaii, Puerto Rico, and international destinations from the continental U.S.
- Travel from September 9, 2025, to March 4, 2026
- Blackout dates: November 20 to 24, 2025; December 18, 2025, to January 6, 2026; and February 12 to 15, 2026
From Hawaii, Puerto Rico, and international destinations to the continental U.S.
- Travel from September 9, 2025, to March 4, 2026
- Blackout dates: November 28 to December 2, 2025; December 18, 2025, to January 6, 2026; and February 20 to 22, 2026
Interisland Hawaii flights
- Travel from September 9 to November 1, 2025
- No blackout dates

Sample Fares

Here’s an example of a discounted ticket from Chicago Midway (MDW) to St. Louis (STL) that you can book for just $39 in Basic and $69 for Choice:

WN MDW STL — Image Credit: Southwest Airlines

Remember, Southwest has an easy-to-use Low Fare Calendar to help you find the cheapest dates when your travel plans are flexible.

Since Southwest Rapid Rewards is a revenue-based program, sales also apply to flights booked using points. Unfortunately, you won’t get outsized value: expect to get around 1.1 to 1.5 cents per point from your Rapid Rewards points.

WN MDW STL points — Image Credit: Southwest Airlines

If you use one of Southwest’s co-branded credit cards to pay for your tickets, you could earn 2 to 4 Rapid Rewards points per $1 spent on your Southwest purchases. These cards also have other perks like anniversary bonus points every cardmember year, EarlyBird Check-In certificates, and more.

Hot Tip:

This sale doesn’t apply to existing bookings, so if you find your same flight is now available at a lower price, you can book it and cancel your existing reservation. Here’s how to change or cancel a Southwest flight.

Recap on Recent Southwest Changes

Remember that Southwest recently introduced basic fares (to replace the previous Wanna Get Away) and ended its popular “everyone gets 2 free checked bags” policy on May 28, 2025. Now, the number of free checked bags you’ll get, if any, depends on what credit cards you hold and whether you have elite status with Southwest Airlines.

Final Thoughts

Southwest is having a flash sale on select routes, advertising flights from $39 one-way if you book by August 21 and travel through early 2026.

Remember that the cheapest fares now book into Southwest’s Basic fare type, and the airline applied its new baggage policy to all bookings made after May 28, 2025. That means you will not automatically qualify for free checked bags when booking the cheapest tickets, and that’s worth considering as you look at prices.