Southwest Airlines usually uses a boarding process that does not depend on assigned seats. Rather, passengers are provided with a boarding group (A, B, or C) and a position number within the allotted group. The Southwest Boarding Order is defined by check-in time, with those checking in earlier receiving earlier boarding positions. The boarding of the groups is first group A, then group B, and then group C. If you want to learn more about the boarding groups, you can contact the Southwest customer service or read the blog by Airlines Group Travel.