AA 9909 then UA 4535 at O'Hare
Waterloo → Chicago → Pittsburgh
Timetable, Chicago time
17:10AA 9909 from Waterloo at the gate
12:48UA 4535 to Pittsburgh leaves the gate
19 h 38 apart on the timetable, overnight
UA 4535 leaves 19 h 38 after AA 9909 arrives on the timetable: more than half a day, so not a connection we count.