Chicago O'Hare International Airport (IATA: ORD, ICAO: KORD, FAA LID: ORD) is the primary international airport serving Chicago, Illinois, United States, located on the city's Northwest Side, approximately 17 miles (27 km) northwest of downtown. The airport is operated by the Chicago Department of Aviation and covers 7,627 acres (11.92 sq mi; 30.87 km2). O'Hare has non-stop flights to 249 destinations in North America, South America, the Caribbean, Europe, Africa, Asia, the Middle East and the North Atlantic region as of summer 2024. As of 2024, O'Hare is considered the most connected airport in the United States, and fifth most connected airport in the world. It is also the world's fourth busiest airport and 16th largest airport. It is the airport with the most runways in the world. Designed to be the successor to Chicago's Midway International Airport, itself once nicknamed the "busiest square mile in the world", O'Hare began as an airfield serving a Douglas manufacturing plant for C-54 military transports during World War II. It was renamed Orchard Field Airport in the mid-1940s and assigned the IATA code ORD. In 1949, it was renamed after aviator Edward "Butch" O'Hare, the U.S. Navy's first Medal of Honor recipient during World War II. As the first major airport planned after World War II, O'Hare's innovative design pioneered concepts such as concourses, direct highway access to the terminal, jet bridges, and underground refueling systems.