Chicago's O'Hare International Airport is at the top of a list of America's busiest airports, according to government statistics released Monday recording the number of flights during the first six months of the year.

Last year's leader, Hartsfield-Jackson Atlanta International Airport, had the second-most flights from January 1 through June 30, according to the Federal Aviation Administration. In third place was Dallas/Fort Worth International Airport.

Both takeoffs and landings are included, according to Tony Molinaro, a spokesman for the FAA.

Chicago and Atlanta have run neck-and-neck in recent years to claim the title of the America and the world's busiest airport. Another commonly cited measure is the number of passengers that pass through a facility each year.

Passenger statistics are not maintained by the FAA, Molinaro said, and were not immediately available for the first six months of 2006.

From January through June 30th, O'Hare Airport registered 477,001 flights, down 1.3 percent from last year but still enough lead the list, according to the FAA.

City officials believe the modest decrease is due to the cap on the number of flights at O'Hare placed by the FAA to help relieve congestion at the airport, said Wendy Abrams, a spokeswoman for the Chicago Department of Aviation.

"We think given the strength of the O'Hare market, it's no surprise that O'Hare is back on top," Abrams said. "It's a key aviation hub both nationally and internationally. From a regional perspective, it offers travelers a gateway to the global economy."

A massive expansion plan getting underway at O'Hare is scheduled to be completed in 2013.

"We look forward to adding much needed capacity at O'Hare to keep pace with expected demand well into the future," Abrams said.

Meanwhile, Atlanta registered 472,431 flights during the first six months of 2006, down 5 percent from the same time last year.

The airport has been affected by airlines cutting down on operating flights that are not full or near full because of high fuel prices, spokeswoman Felicia Browder said.

She also noted that Delta Air Lines Inc., which operates the most flights at the airport, has been ramping up its international operations while ramping down its domestic operations.

"It will take some time for our flight operation numbers to rebound while they do that," Browder said.

Even so, Browder noted that the Atlanta airport traditionally has been the busiest airport in terms of passengers, and she expects that to remain the same this year.

In third place on the FAA list was Dallas/Fort Worth International Airport, where 348,434 flights landed or took off through June of this year, down 2.1 percent from the same time period last year.