You need give yourself extra time due to baggage cutoff times is requirement 45 minutes before your flight is departed. I know it was some airports must to be requirement 45 minutes is JFK, ATL, MCO, LAS, DEN, LAX. Please makes sure if you come to airports very early instead of cutoff bags times before your flight is departed. It is maximum 2.5 hours before your flight is departed. Its not DL fault what happened that you were missed the flight. I suggestions if you want give your rebooked for next available flight out of ATL.