In 2026, the cheapest days to fly on Southwest Airlines consistently remain Tuesdays and Wednesdays. These mid-week days see the lowest demand from both business travelers and vacationers, prompting the airline to lower fares to fill seats. While Southwest is famous for its "Wanna Get Away" fares, they also frequently launch three-day sales on Tuesday mornings, which can drop prices significantly for those specific days. Traveling on a Saturday or a "dead" period—such as the first two weeks of December or late January—can also yield low prices. Conversely, Fridays and Sundays are almost always the most expensive due to the high volume of weekend travelers. To find the absolute lowest fare, Southwest’s "Low Fare Calendar" tool is indispensable; it allows you to view a whole month of pricing at once, often revealing that shifting your departure by just 24 hours can save you $50 to $100 per person. Always aim to book at least 21 days in advance to capture the best tier of discounted tickets.