AA 4102 then UA 5191 at O'Hare
Denver → Chicago → Lancaster
Timetable, Chicago time
12:55AA 4102 from Denver at the gate
08:50UA 5191 to Lancaster leaves the gate
19 h 55 apart on the timetable, overnight
UA 5191 leaves 19 h 55 after AA 4102 arrives on the timetable: more than half a day, so not a connection we count.