ATLANTA (AP) _ Hartsfield Atlanta International edged Chicago's O'Hare for the first time in 1987 to become the world's busiest airport, a Federal Aviation Administration official said Thursday.

The rankings are based on FAA statistics through midnight Wednesday, plus estimates for Thursday's traffic. Hartsfield had an estimated 797,037 flights to O'Hare's 794,921 takeoffs and landings.

The Atlanta airport handled an average of about 15 more takeoffs and landings per day than O'Hare, said Jim Wright, FAA division manager for air traffic in Atlanta.

O'Hare ''had it all to themselves for a long, long time, but we've sneaked up on them,'' he said, adding that traffic controllers at Hartsfield keep track of the numbers throughout the year.

''There is a strong competition,'' he said. ''There's a lot of pride in being No. 1 in the college football polls or basketball polls or air traffic.''

''The prestige factor is very important,'' said Susan Neugent, director of regional development for the Atlanta Chamber of Commerce. ''It does mean a lot when you can say you're No. 1.''

Marjorie Kriz, an FAA spokeswoman in Chicago, said, ''We had to close down Dec. 15, and on two days we had two-thirds of the flights canceled because of weather. And it flooded so much last summer that O'Hare literally became an island.

''Besides, our football team is in the playoffs.''