AA 4783 then UA 5191 at O'Hare
Baltimore → Chicago → Lancaster
Timetable, Chicago time
12:59AA 4783 from Baltimore at the gate
08:50UA 5191 to Lancaster leaves the gate
19 h 51 apart on the timetable, overnight
UA 5191 leaves 19 h 51 after AA 4783 arrives on the timetable: more than half a day, so not a connection we count.