Southwest Airlines compiles fare data from its reservation system, capturing every fare class offered on each flight. The calendar aggregates this information over a 30‑day window, assigning green, yellow, or red shading to indicate low, moderate, or high price tiers relative to the route’s average.
Travelers can toggle between one‑way and round‑trip views, select specific airports, and filter by departure time. By spotting contiguous green cells, users pinpoint optimal departure windows; the calendar also flags fare sales that may appear briefly before seats fill.