AA 642 then UA 5199 at O'Hare
Dallas-Fort Worth → Chicago → Denver
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
08:30UA 5199 to Denver leaves the gate
19 h 20 apart on the timetable, overnight
UA 5199 leaves 19 h 20 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.