It's different year to year, we go in February and have found direct flights sometimes as seen here https://www.google.com/flights/#flt=...D;e:1;sd:1;t:f. Maybe an hour and a half layover in Atlanta. 300 days out from our trip I go to google flights and start looking every couple/few days. It gives you airline options and of course pricing for your dates. We've booked many months in advance when we find a decent flight at a decent price.