Southwest is the US's fourth-largest operator by passengers. However, as the US Department of Transportation shows that 98% of its traffic is domestic, it is the nation's third-largest domestic carrier. Southwest carried one in five of all passengers who flew within the country.

In the 12 months to August 2025, the DOT shows that Southwest filled 77.8% of its available seats . This was obviously disproportionately driven by its enormous dominance domestically. Indeed, it filled 83% of its international capacity.

Southwest's Routes With The Lowest Loads

Analysis of all the airline's network between September 2024 and August 2025 shows that the following ten routes had the lowest seat load factors . As always, caution must be given when discussing this topic.

Loads are

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