what did I miss in there?
he can spend money to change his flight with delta or if and only if (small chance in my opinion)he misses his next flight due to weather or IRROPS into ATL he will spend money to change his next flight....
I contend that often times in this situation his next airline will be understanding of the situation that cause this and not charge him to reschedule him. Delta often times can assist with this if there is IRROPS or weather, in my experience they have even called the other airline to explain the situation and the other airline was very accommodating.