Chicago Midway International Airport — Chicago, United States

Chicago Midway International Airport (MDW) held the title of the world's busiest airport for a stretch of the mid-twentieth century before O'Hare eclipsed it, and it remains Chicago's second major airport today, hemmed tightly into a dense residential grid on the city's southwest side. Its compact footprint gives MDW notably short runways by big-city standards, a layout that has occasionally factored into overrun incidents, including a widely reported 2005 accident in which a landing aircraft slid through a barrier onto an adjacent street. Southwest Airlines has long treated Midway as one of its most important bases, operating the majority of flights from the airport and shaping its identity as a low-cost, primarily domestic hub. Unlike sprawling O'Hare, Midway retains a single consolidated terminal, giving it a reputation among travelers for faster curb-to-gate transit despite its smaller scale and older infrastructure.