Hartsfield-Jackson International Airport is preparing to hit a milestone never before reached by any airport in the world: 100 million passengers in a year.

The 100 millionth passenger is expected to pass through the Atlanta airport in the next three to four weeks, said Hartsfield-Jackson general manager Miguel Southwell.

“For the first time in history, an airport will have 100 million passengers. That’s something only Atlanta can claim,” Southwell said. The airport has hired accounting firm KPMG to “help validate this milestone,” he said.

There’s no single entryway that all passengers pass through at an airport to be counted. Instead, the accounting firm will help the airport target the week and as close as possible to the day that it will cross the 100 million threshold, then a passenger will be selected from that day, according to airport spokesman Reese McCranie.

The world’s busiest airport plans to celebrate that 100 millionth passenger in some yet-to-be-determined way.

Last year, as flight counts decreased as airlines replace smaller planes with larger ones to carry more passengers, Chicago O’Hare surpassed Atlanta as the airport with the most flights, while Atlanta still had the most passengers in the world.

But this year, Atlanta has had an increase in flight counts, along with a 5 percent increase in passengers.

For the year through October, Chicago O’Hare reports it has handled 735,742 flights and nearly 64.6 million passengers. In the same time period, Atlanta reports it has handled 737,463 flights and nearly 84.8 million passengers.

With record crowds expected to stream through Hartsfield-Jackson over the holidays, the airport is adding more live music and roving carolers in the airport.

Southwell said the airport will also add more entertainment in the terminal throughout the year.