Southwest Airlines is a domestic U.S. passenger airline flying passengers between cities primarily within the U.S., with a smaller presence in near-international markets (Mexico, the Caribbean, and Central America). As of year-end 2025, Southwest operated 803 Boeing 737 aircraft serving 117 destinations. Southwest sells tickets directly to consumers primarily through its own website and app, and increasingly through online travel agencies and flight search aggregators. Southwest also sells to corporate travel customers through its SWABIZ platform and global distribution systems. Southwest earns revenue by selling airline seats and ancillary services, and manages revenue through RASM (revenue per available seat mile), which reflects both how full planes are and how much each passenger pays. Southwest's cost structure has historically been a competitive advantage, driven by labor (~47% of operating expenses), fuel (~19%), and a single-aircraft-type fleet (all Boeing 737s), which simplifies maintenance, training, and scheduling. Southwest is in the middle of a significant business model transformation — historically differentiated by open seating, two free checked bags, no change fees, and low fares, Southwest has overhauled nearly every element of this model. Key changes include introducing bag fees, basic economy, assigned and extra legroom seating, variable loyalty earn/burn rates, and flight credit expiration. These initiatives shift Southwest from a historically undifferentiated model to a more segmented one, bringing Southwest closer to the approach major network carriers use. The Rapid Rewards loyalty program and Chase co-branded credit card are also important revenue contributors.