(CNN) — Look out. The bragging war between two of the world's busiest airports just got more intense.

For the first time in a decade, Chicago's O'Hare topped Atlanta's Hartsfield-Jackson in total flights by more than 13,000, according to new stats from the U.S. Federal Aviation Administration.

The score for 2014: Chicago, 881,933; Atlanta, 868,359.

Hey, this is important. It's about who's No. 1. It's about bragging rights.

"Chicago reclaims its place" as the "world's busiest airport," Chicago Mayor Rahm Emanuel said in a statement Thursday, crediting new airline routes, newly relocated businesses and the city's strong economy.

But Atlanta's Hartsfield-Jackson remains No. 1 in annual passenger traffic. Spokesman Reese McCranie said the airport is projected to top 96 million passengers for 2014, compared with O'Hare, which handled 66.7 million in 2013 . That put O'Hare in fifth place globally for passengers.

"With our friends in Chicago, it's always a little bit of friendly rivalry," McCranie said. "Our operations folks are probably getting ribbed by their operations folks for edging us out. But you know, we're all one aviation system, so when O'Hare does well, other airports -- including ours -- do well."

For the first time in a decade, Chicago O'Hare overtook Atlanta Hartsfield-Jackson in takeoffs and landings. China's Beijing Capital airport is rapidly climbing.

So really, which airport is the busiest? Which is more challenging for an airport? Handling more airplanes -- or more passengers?

Each has its own contributing factors:

- Atlanta tends to have more sunshine than Chicago, which may cut weather delays and cancellations.

- O'Hare hosts many regional airlines, but McCranie said Atlanta carriers are adding more airliners with higher passenger capacity.

"So when you have that, of course that means you don't have as many takeoffs and landings," McCranie said.

Chicago's O'Hare International Airport handled 881,933 takeoffs and landings in 2014, according to the FAA, more than any airport in the world. Thinkstock

Let's stop for a minute and remind ourselves that these two airports are called upon to perform something that's really quite amazing. With incredible attention to safety, they serve nearly a million flights a year and tens of millions of passengers.

Large international airports are among the world's most complicated facilities, with constantly moving components that require detailed attention. Being the busiest -- on any level -- is a true badge of honor.

Emanuel said the victory comes from Chicago being "the top metro area for foreign direct investment" and its "record growth in international tourism."

So, how do you define the world's "busiest" airport? What's the definition of "busy?" Webster's makes it pretty simple: "actively doing something."

From a traveling consumer perspective, traditionally, passenger traffic has been the key stat when talking about the "busiest" airports.

That's because the FAA takeoff and landing stats include military and other noncommercial flights. For example, an airport that includes a hub for a cargo delivery outfit -- such as UPS Airlines in Louisville, Kentucky -- is going to have more takeoffs and landings that don't include passengers.

Chicago's O'Hare International Airport has a program to help at risk students prepare for the working world.

Although 2014 global stats are pending, year-to-date figures suggest that Atlanta will still be the busiest airport in the world based on passenger traffic, according to Airports Council International.

In 2013, ACI said Beijing ranked No. 2 in passengers, with 83.7 million.

Passenger discovers alligator at Chicago O'Hare Airport.

The rising passenger traffic at Dubai's airport shows how aviation's "nucleus" has moved eastward in the past decade, resulting in double-digit growth rates, said Dr. Rafael Echevarne, ACI economics director. Airlines, he said, are scheduling more fights out of Dubai that use wide-body, long-haul planes that carry more passengers.

As for airport takeoffs and landings in 2013, it ranks globally like this (after Atlanta and Chicago):

3. Los Angeles; 696,443

4. Dallas-Fort Worth; 678,059

5. Denver; 582,653

6. Beijing; 567,759

Meanwhile, these new numbers appear to be throwing more fuel on the fire in the rivalry between Atlanta Hartsfield-Jackson and Chicago O'Hare.