Southwest Airlines operates the simplest mainline fleet of any major American carrier. It is also, by number of aircraft, one of the largest. As of 2026 Southwest flies around 800 aircraft, all of them variants of the Boeing 737. No other major carrier in the world has committed as thoroughly to a single aircraft type, and the commitment is a structural part of how Southwest has operated for nearly five decades.

This is a guide to every aircraft Southwest flies and why the airline's all-737 strategy still works.

The fleet

Boeing 737-700. The 737-700 has been a core part of Southwest's fleet since the 1990s. It seats 143 passengers in Southwest's single-class configuration and is used on shorter routes where the -800 would be oversized. Southwest has been gradually retiring its 737-700 fleet as 737 MAX 8 deliveries arrive, but the -700 is still in active service and expected to remain so into the late 2020s.

Boeing 737-800. The 737-800 entered Southwest's fleet in 2012, marking the first time the airline operated a 737 variant larger than the -700. The aircraft seats 175 passengers and became a major part of Southwest's capacity growth strategy through the 2010s. As of 2026, the 737-800 is still the airline's most common single aircraft type.

Boeing 737 MAX 8. Southwest is one of the largest 737 MAX 8 operators in the world. The airline was an early customer and operated the aircraft through the 2019-2020 grounding and return-to-service. The MAX 8 seats 175 passengers in Southwest's configuration, the same as the 737-800, but offers around 14 percent better fuel efficiency. New MAX 8 deliveries have been the main source of fleet growth since the return to service.

Boeing 737 MAX 7. Southwest was the launch customer for the MAX 7 variant, which is the shorter sibling of the MAX 8. The MAX 7 will eventually replace the 737-700 fleet on lower-density routes. As of 2026 the aircraft is still awaiting FAA certification, with entry into service expected imminently. Southwest has a large order book for the type.

Why Southwest flies only the 737

Southwest's single-fleet strategy is one of the most-discussed choices in commercial aviation. Operating a single aircraft type has enormous operational advantages. Pilot training is simpler because pilots only need to be qualified on one aircraft type. Maintenance is simpler because the airline only needs to stock parts and train mechanics for one platform. Crew scheduling is more flexible because any pilot can fly any aircraft in the fleet. Ground operations are standardized because every plane has the same door configuration, catering setup, and cabin layout.

The disadvantage is that Southwest is locked into the 737. When Boeing has problems with the 737 family, as it did during the MAX grounding and subsequent quality issues, Southwest has no alternative aircraft to shift capacity to. When Airbus launched the A321neo as a long-range narrowbody, Southwest could not participate in that market because it does not fly Airbus aircraft. The airline has, at various points, studied whether to add a second type, and has consistently concluded that the operational savings of single-type operations outweigh the commercial limitations.

Southwest's route network is also designed around the 737's capabilities. The airline flies point-to-point rather than hub-and-spoke, operates mostly short-to-medium-haul routes, and does not serve long-haul international markets. The 737 is a perfect fit for this operation. A fleet optimized for transatlantic or transpacific flying would require widebodies Southwest does not need.

The seating experience

Every Southwest aircraft has a single-class cabin, with no first class or business class. Seat pitch is around 32 inches across the fleet, which is slightly better than most low-cost carriers but less than premium economy on a legacy airline. The aircraft have overhead bins sized for standard carry-on luggage and in-seat power in most newer deliveries.

One feature of Southwest that is changing in 2025 and 2026 is the seating assignment system. Historically, Southwest did not assign seats. Passengers boarded in a numbered sequence based on check-in time and chose whatever seat was available. The airline announced in 2024 that it would move to assigned seating, following the pattern of other American carriers, and the rollout is currently underway.

What to expect when booking

Because the fleet is so uniform, the aircraft type on a Southwest flight is less predictive of the experience than it would be on American or Delta. Every flight has the same seating product, the same service, and the same general flight experience. The specific variant matters mainly for range: flights under two hours are more likely to be on a -700, flights across the continental US or to Hawaii are more likely to be on a -800 or MAX 8.

Southwest serves about 121 destinations as of 2026, primarily in the United States, with service to Mexico, Central America, the Caribbean, and Hawaii. The 737 family is capable of all of these routes. The airline does not fly to Europe, South America, or Asia, and its all-737 fleet reinforces that geographic focus.

Fleet comparison

Southwest's choice to operate only the 737 stands in contrast to other major American carriers. American Airlines operates a mix of Airbus and Boeing narrowbodies plus Boeing widebodies. Delta flies Airbus narrowbodies, Boeing narrowbodies, and Airbus widebodies. United has a Boeing-heavy fleet with a growing Airbus narrowbody presence. All three legacy carriers spend more on fleet complexity than Southwest does, and all three have more operational flexibility in exchange.

The single-fleet strategy is unusual, but it is not unique. Ryanair in Europe and Wizz Air on the Airbus side of the market follow similar approaches, with nearly-identical fleets that enable cost leadership. These airlines have built their competitive positions around the efficiency of single-type operations. Southwest is the original practitioner of the strategy in the United States, and the approach has defined the airline for most of its history.

If you fly Southwest, you are almost certainly on a 737. Whether it is a -700, -800, or MAX 8 depends on the route, but the difference is largely invisible to the passenger. The cabin is the same, the service is the same, and the airline's entire operational model is designed around that uniformity.