AA 642 then UA 2844 at O'Hare
Dallas-Fort Worth → Chicago → St Louis
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
10:45UA 2844 to St Louis leaves the gate
21 h 35 apart on the timetable, overnight
UA 2844 leaves 21 h 35 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.