TSA recommends arriving 2 hours before a flight. But for ATL specifically, it is the busiest airport in the U.S. with an annual passenger count of over 100 million according to worldatlas.com. Therefore we recommend giving yourself an additional 45 minutes to an hour to the normal 2 hour arrival time. Read more specifics about ATL being the busiest airport in the U.S. here: https://www.worldatlas.com/articles/busiest-airports-in-united-states.html