AA 642 then UA 2809 at O'Hare
Dallas-Fort Worth → Chicago → Dallas-Fort Worth
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
10:40UA 2809 to Dallas-Fort Worth leaves the gate
21 h 30 apart on the timetable, overnight
UA 2809 leaves 21 h 30 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.