This is just my opinion, so take it as you like....
I have flown on several airlines. The rule is to be at the airport 3 hours in advance for an international flight and 2 hours for a flight to a destination in the US. Since you are flying to Atlanta, you fall in the 2 hour group.
With all that is going on in air travel and around the world, I would be there 2 hours in advance just so I could be relaxed and certain that I'm at the airport, checked in and through security in plenty of time. We were going to Orlando (early one Sunday morning) and didn't sweat being late. We arrived 2 hours in advance only to find that I had missed on the news that all flights had been canceled the day before because of a wind/sand storm. We missed our flight because we could not get through checking in and security in enough time.
Another time, we arrived 2 hours in advance, but a lot of other people had chosen to fly at 7 am Sunday morning. We barely got through security and walked on to the plane, at the last minute. I don't like cutting it that close.
Try getting there early and if you have extra time, walk through the shops or have a meal, or even buy a snack to eat on the plane. It is so nice to start your trip in a relaxed state instead of worrying about what you will do if you miss your flight.
Have a great time!