Southwest Airlines plays a critical role in US aviation. Between March 2025 and February 2026, the country’s Department of Transportation (DOT) shows that it transported 170 million passengers. However, compared to the prior 12 months, traffic fell by nearly 4.7 million passengers. Its overall load factor (which is technically the seat factor) was 77.4%.

Nearly one in six of the nation’s passengers flew the increasingly evolving carrier, which rose to one in five for the vast domestic market. Southwest recently gave more details about its long-haul ambitions, along with the plan for domestic first class and more. The airline, which is now a self-described hybrid operator, just began its new longest nonstop service within the Lower 48.

Southwest’s Worst-Performing Route By Load Factor

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DOT data has been used to examine all of Southwest’s routes, both domestic and international, operated at any point between March 2025 and February 2026. This process identifies each market’s load factor. As usual, loads should not be considered in isolation. Unless they are exceptionally low, which would speak volumes, it is critical to understand how they were achieved.

With just 38.0% of seats filled, Islip to Miami was Southwest’s worst-performing route in this sense. Some 17,921 round-trip passengers were carried, but the amount of capacity available, from its daily service, was far too great for the traffic achieved.

Cirium Diio data shows that Southwest only served this market between November 2024 and August 2025. It is hardly surprising that it has ended. When Frontier Airlines operated between 2017 and 2021, it only filled 61.4% of seats, despite the DOT showing an average fare of just $30 one-way (excluding taxes and add-ons). In contrast, it was $175 for Southwest. Will another airline attempt to make it work? That’s currently hard to imagine.

Southwest’s Routes With The 2nd To 5th-Lowest Loads

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They’re summarized in the following table. All filled fewer than one in two of the available seats, which was substantially lower than the carrier’s system load of 77.4%. With a paltry result of 41.5%, Kahului Airport (OGG) to Lihue ranked second-to-last. Southwest has served the market, which covers just 175 nautical miles (324 km) each way, since 2022. Despite the poor result, flights continue to operate.

Southwest’s operations within Hawaii have often performed poorly. It has been part of the airline’s network since 2019. Between March 2025 and February 2026, all these routes collectively carried 1.8 million passengers. However, just 56.7% of seats were filled. Compared to the previous 12 months, the DOT shows that traffic rose by 4% while the number of seats for sale fell by 16%. This contributed to the overall intra-Hawaii load rising by nearly 11 percentage points — but it remains very low.

Southwest’s 6th To 10th-Lowest Loads

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With a load factor of just 49.3%, Palm Beach, which is seemingly being renamed after Donald Trump, to Orlando International Airport (MCO) ranks sixth (67,128 round-trip passengers). This route only covers 122 nautical miles (226 km) each way.

Launched in August 2025, it exists virtually entirely for passengers to fly elsewhere via MCO. The DOT indicates that 92.2% of passengers connected to another flight in MCO. It is one of many new very short airport pairs from MCO, Nashville, Chicago Midway, Denver, and so on, which exist for passenger connectivity reasons.

The seventh-lowest result, Sarasota to MCO, is in the same boat (51.4%; 64,688 passengers); flights started last August. Then there’s OGG to Kona (51.8%; 66,447 passengers), Washington National to Columbus (52.3%; 54,321 passengers), and Atlanta to Greenville/Spartanburg (52.6%; 6,793 passengers; ended in April 2025). Due to many cuts over the past few years, as Southwest focuses on where it can win, Atlanta is now only the carrier’s 21st most-served airport for flights.