OO 9909 then AA 4748 at O'Hare
Waterloo → Chicago → Pittsburgh
Timetable, Chicago time
16:47OO 9909 from Waterloo at the gate
09:45AA 4748 to Pittsburgh leaves the gate
16 h 58 apart on the timetable, overnight
AA 4748 leaves 16 h 58 after OO 9909 arrives on the timetable: more than half a day, so not a connection we count.