Charlotte Douglas International Airport — Charlotte, United States

Few airports illustrate the power of a single dominant carrier better than CLT, where American Airlines (and before it, US Airways and Piedmont Airlines) built a connecting hub that now ranks among the busiest airports on the planet by aircraft movements. The airport's name honors Ben Elbert Douglas, a Charlotte mayor whose early-20th-century advocacy helped establish municipal aviation infrastructure in the Carolinas. Charlotte's emergence as a major banking and finance center over the past several decades paralleled the airport's own growth, and today CLT's four parallel runways manage an enormous volume of connecting traffic funneling passengers between the Northeast, Florida, and the rest of the Southeast, plus a growing slate of transatlantic routes to Europe. Cargo operations, including a significant express-package sorting facility, add another layer of activity beyond passenger flights. Despite its immense traffic volumes, the airport retains a reputation for relatively efficient connections, a legacy of decades spent optimizing hub-and-spoke scheduling for the carriers that have called it home.