Here’s a tiny hack that might help you get a better seat on your return trip when flying Southwest Airlines roundtrip in a single day.
Southwest Airlines does not assign seats, and follows an open seating model.
Customers board in order of the group (A, B, or C) and number (one to sixty) on their boarding pass. The earlier you check in, up to 24 hours prior to your flight, the earlier your assigned spot in line.
Group A boarding passes put you at the front of the line, increasing the likelihood that you can sit with your travel companions, and giving you the best chance for a window or aisle seat.
Cool Tools has a neat trick to up your chances of getting Group A boarding passes for both legs of your trip when flying out and back on the same day.
As Cool Tools notes,
If you book a one-day round trip on Southwest, you won’t be allowed to check in for the return flight until after you complete the first flight.
However, if you book two one-way trips instead of a round trip, you can check in for both flights exactly 24 hours before the scheduled departure.
Two one-way tickets are priced identically to a round-trip ticket, so there is no extra cost to pursuing this strategy.