Long lines for airport security screening stretched through the domestic terminal and snaked through baggage claim at Hartsfield-Jackson International on Monday.
Wait times were more than an hour long during a busy period of the morning, according to the Atlanta airport's website.
The airport on its website is now advising travelers to get to the terminal three hours before their flight.
The lines early Monday morning stretched from the main security checkpoint through the atrium, around the corner, winding back and forth between baggage claim carousels, then down the hallway of the domestic terminal.
The Transportation Security Administration last week closed the Terminal South security checkpoint at Hartsfield-Jackson for a three-week stretch, as it redesigns two of the lanes to test a system that is aimed at speeding screening.
But in the meantime, the tens of thousands of travelers that fly out of Hartsfield-Jackson every day are being added to the already-congested main checkpoint and the Terminal North checkpoint in the domestic terminal.
Airport officials have raised concerns about long security screening lines, which have stretched into baggage claim during busy periods for the past year.
Monday mornings are one of the busiest periods at the world's busiest airport, with business travelers leaving for weekly trips adding onto the thousands of other passengers.
TSA officials have said workers who staffed the closed checkpoint are now helping to staff the main checkpoint, so lines are long but will move more quickly.