Chicago Midway International Airport

Chicago Midway International is Chicago's secondary commercial airport and one of the most concentrated single-carrier operations in North America: Southwest Airlines accounts for roughly 90% of MDW's seats and traffic, making Midway the airline's largest single station. MDW serves 239 destinations across 33 airlines in the global route graph, a count inflated by the density of Southwest's point-to-point map that radiates outward from Midway across the continental U.S. The airport occupies exactly one square mile (640 acres) at 55th Street and Cicero Avenue on Chicago's southwest side — an urban-grid footprint so constrained it is still the world's busiest airport by operations per acre, and its compact size permanently limits expansion. The four runways (6,522 ft / 1,988 m and shorter) are too short for most long-haul widebody operations, which routes international long-haul through O'Hare and leaves Midway as a pure domestic and near-international (Mexico, Caribbean) operation. Frontier, Delta, and Volaris maintain secondary operations alongside Southwest's dominant schedule. MDW sits at 620 ft (189 m) elevation on the Bedford Park border 12 miles (19 km) southwest of the Loop. Midway's historic significance precedes its Southwest era: through most of the 1930s–1950s it was the world's busiest airport, a title it lost only when O'Hare opened in 1955 and the jet age required longer runways than Midway's one-square-mile plot could provide. The modern terminal complex, expanded in 2004 and further upgraded in 2018, concentrates operations in a single landside terminal feeding three concourses (A, B, C). Connection to downtown Chicago via the CTA Orange Line makes Midway one of the most transit-accessible U.S. airports for a secondary operation.