What does O'Hare's nickname "Windy City Airport" refer to?

The nickname "Windy City Airport" indeed refers to Chicago's historical weather patterns and winds. This nickname stems from the windy conditions that are commonly experienced in the area, which are influenced by its geographical location near Lake Michigan. The term "Windy City" has often been associated with Chicago itself, highlighting its breezy weather, especially during certain seasons.

While the other options may seem plausible, they do not accurately capture the essence of the nickname. The reference to high traffic and a busy atmosphere speaks to the airport's operation but does not connect to the wind-related aspect of the nickname. Similarly, the expansive runways or the presence of wind tunnels, while relevant to aviation and airport design, do not relate to the historical context associated with the term "Windy City." Understanding this nickname is rooted in the climatic characteristics of the city helps clarify the cultural and historical significance attached to it.