New figures from the Federal Aviation Administration show Chicago's O'Hare International Airport remains the second busiest in the nation.
Atlanta's Hartsfield-Jackson is the busiest by number of arrivals and departures, despite a decline of 2.7 percent in 2011 from the previous year.
Traffic was also down at O'Hare, dipping 0.4 percent to nearly 879,000 takeoffs and landings. The figures were released Thursday by the Federal Aviation Administration.
Worldwide, O'Hare ranks third busiest by passenger numbers behind Atlanta and Beijing.
O'Hare is undergoing a $15 billion expansion.
The city reached a deal in March with United and American airlines on funding for a second phase of expansion involving construction of a new runway and other upgrades. Under the deal, Chicago issued $1 billion in bonds to pay for the work.