AA 642 then UA 777 at O'Hare
Dallas-Fort Worth → Chicago → Las Vegas
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
12:47UA 777 to Las Vegas leaves the gate
23 h 37 apart on the timetable, overnight
UA 777 leaves 23 h 37 after AA 642 arrives on the timetable: more than half a day, so not a connection we count.