AA 642 then UA 1878 at O'Hare
Dallas-Fort Worth → Chicago → Burlington (BTV)
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
11:00UA 1878 to Burlington (BTV) leaves the gate
21 h 50 apart on the timetable, overnight
UA 1878 leaves 21 h 50 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.