AA 642 then UA 4791 at O'Hare
Dallas-Fort Worth → Chicago → South Bend
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
10:25UA 4791 to South Bend leaves the gate
21 h 15 apart on the timetable, overnight
UA 4791 leaves 21 h 15 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.