An increase in flights this year has helped O’Hare International Airport narrow the gap with arch-rival Atlanta for the title “world’s busiest airport,” and air-traffic controllers in Chicago predict O’Hare will soon retake the top spot with help from a new runway opening this fall.

Hartsfield-Jackson Atlanta International Airport wrestled the top honor away from O’Hare in 2005 and has retained it ever since, according to the official flight count by the Federal Aviation Administration.

O’Hare previously had bragging rights to the title since the dawn of the Jet Age, when it surpassed Midway Airport, which had been the leader.

In the first six months of 2013, Atlanta handled 453,800 takeoffs and landings, while O’Hare accommodated 426,800 flights, a preliminary FAA tally shows.

Atlanta has also topped O’Hare in the number of passengers served annually in recent years. A preliminary passenger count for the first half of 2013 is not yet available.

Despite the 27,000-flight cushion for Atlanta so far this year, an increasing volume of flights at O’Hare over the last two months is trending to make it a horse race.

In May and June, Atlanta had a total of 157,000 flights to O’Hare’s 154,200, for a difference of only 2,800 flights over the two months.

For the full 2012, a total of 930,098 flights operated at Atlanta, versus 878,108 at O’Hare, FAA statistics show.

O’Hare’s busiest year on record was in 2004, when the airport handled 992,471 flights, the FAA said. O’Hare hasn’t flirted with 1 million flight operations since then.

Among the nation’s 29 busiest airports this year through May, O’Hare had the second-worst on-time performance for arriving flights, with three out of 10 flights parking at the gate late. Atlanta posted the sixth-best rate, with 84 percent of arrivals on time, according to the U.S. Bureau of Transportation Statistics.

O’Hare’s capacity to handle more flights will increase starting in mid-October when the next new runway opens, as part of the city of Chicago’s O’Hare Modernization Program.

Asked whether he was going to repost a sign that says “world’s busiest” on the door to the air-traffic tower cab at O’Hare, Bob Flynn, the FAA’s tower manager at the airport, said: “It’s already on the door, don’t worry.”

Chicago’s goal is to grow the number of O’Hare flights, while also reduce delays that make O’Hare unpopular among some fliers.

The runway expansion plan, when completed, would feature six parallel runways in an east-west layout and two crosswind runways, lining up northeast to southwest. The format replaces a pattern of intersecting runways.

Atlanta, which opened its fifth runway in 2006, has no plans pending for more runways, the FAA said.

The O’Hare runway set to open on Oct. 19, called 10 Center/28 Center, will serve as an arrival runway and enable O’Hare controllers to use three arrival runways, instead of only two, in reduced visibility, according to the FAA.

The runway opening marks a shift to a predominantly west flow and east flow of planes to the airport, officials said. It will also bring an increase in airplane noise over some suburbs and areas of Chicago, the Tribune reported in April. Areas to the north and south of the airport are expected to experience less noise, while areas to the east and west are expected to experience more.

The city has received a funding commitment from the airlines to build one more runway after that, on the far south end of the airfield on land that Chicago acquired from Bensenville. The runway is scheduled to open in 2015, according to the Chicago Department of Aviation.

No agreement has been reached on the city’s plan to build a final runway north of the passenger terminals, nor to lengthen an existing runway.

Negotiations between the airlines and the Emanuel administration were to resume this past spring, but no progress has been made. United Airlines and American Airlines insist that future decisions will be guided by customer demand for more flights.

Mayor Rahm Emanuel has said he wants to complete the more than $9 billion O’Hare expansion project now, to avoid a further escalation of costs.

Photo Credit: A Delta Airlines plane is seen at O'Hare International airport in Chicago. Frank Polich / Reuters