The cheapest day to buy Southwest Airlines tickets is typically Tuesday or Wednesday. Airlines, including Southwest, often release sales on Monday evenings, which can lead to lower fares being available on Tuesdays and Wednesdays. This is because many airlines adjust their prices to match or compete with those sales. It’s also worth noting that booking flights several weeks in advance tends to yield better prices. Additionally, flying on certain days (like Tuesdays, Wednesdays, or Saturdays) can often be cheaper than flying on busier days like Fridays or Sundays