If a flight has few seats left, Southwest's website will show the number of seats left below the price in small, red text. But these are the only seats remaining under a certain fare class, not necessarily the last seats on the plane.

Southwest Airlines does not publicly display the exact number of remaining seats on their website or app. However, a clever "hack" used by travelers in 2026 involves the booking quantity method: go through the process of booking a new flight and select "8 passengers" (the maximum allowed). If the system allows you to proceed to the payment screen, there are at least 8 seats left. If it says "only 3 seats left at this price," you know the flight is nearly full. Another indicator is the fare type availability; if only high-cost "Choice Extra" (Business Select) seats are available and "Basic" (Wanna Get Away) is grayed out, the plane is likely over 90% full. Note that with Southwest's transition to assigned seating in early 2026, you can now view the seat map during the booking process for most fares, giving you a visual representation of how many spots are truly unoccupied.