O'Hare International Airport is still a bridesmaid to its counterpart in Atlanta but narrowed the gap between the two in 2013 when it comes to the world's busiest airport title.
O'Hare handled 883,287 flight operations last year, compared to Hartsfield-Jackson Atlanta International Airport's 911,074, a 27,787 difference. But in 2012 Atlanta chalked up 51,990 operations more than O'Hare.
From July through October of 2013, O'Hare was briefly the nation's busiest airport, surpassing Atlanta by 4,243 flights.
The shift is partially attributable to a dip in operations at Atlanta Hartsfield, which were down by 2 percent in 2013. O'Hare traffic actually increased only incrementally in 2013, up by 0.6 percent or 5,179 operations.
"For every winner, there's a loser," DePaul University aviation expert Joseph Schwieterman said.
"That gap (between O'Hare and Atlanta) was sizable for years ... the trends are once again in Chicago's favor."
Midway Airport traffic also experienced an uptick with 252,126 flight operations compared to 249,913 in 2012, a 1 percent difference. Overall, Midway ranked 26th busiest out of 45 U.S. major airports.
"These numbers mirror the investments in new runways," said Schwieterman, director of DePaul's Chaddick Institute for Metropolitan Development. O'Hare added a runway in fall 2013.
"We're finally seeing all the big projects pay dividends. It's also good news that American and United (airlines) are on solid financial footings -- it's been a while since you could say that."
Airline mergers between United and US Airways and American and Continental Airlines should also push demand up, Schwieterman thinks. "It reminds me of the 1990s, when American and United pushed for market share." The carriers will likely up the ante with an increase in international flights, he predicted.
Following Atlanta and O'Hare in order as the top 10 busiest airports were Dallas/Fort Worth International Airport, Los Angeles International Airport, Denver International Airport, Charlotte Douglas International Airport, Las Vegas' McCarron International Airport, Houston's George Bush Intercontinental Airport, Phoenix Sky Harbor International Airport and Philadelphia International Airport.