What is the airport code for Chicago, Illinois (O'Hare Airport)?

The airport code for Chicago O'Hare International Airport is ORD. This code comes from the airport's original name, "Orchard Field," which was established during World War II. O'Hare is one of the busiest airports in the United States and serves as a major hub for American Airlines.

In this context, the other options do not correspond to O'Hare Airport. CHS is the airport code for Charleston International Airport in South Carolina, CMI refers to Central Illinois Regional Airport in Bloomington, and CUN is the airport code for Cancun International Airport in Mexico. This helps to underscore the unique identifier that ORD represents specifically for O'Hare in Chicago.