Chicago's O'Hare International Airport is the nation's busiest airport.
O'Hare had more than 477-thousand flights during the first half of 2006.
Hartsfield-Jackson Atlanta International Airport was second, with more than 472-thousand take-offs and landings.
The Federal Aviation Administration says Dallas/Fort Worth International Airport was the third busiest.
Atlanta argues that it is consistently the nation's busiest airport in terms of passengers.
While busy, O'Hare saw a one-point-three percent decrease in flights. Chicago officials attribute that to an FAA-imposed limit on the number of flights at O'Hare to help relieve congestion there.
Atlanta had five percent fewer flights compared to the same time last year. A spokeswoman notes that the airport has been affected by airlines cutting down on flights that are not full or near full because of high fuel prices.