AA 6365 then UA 5901 at O'Hare
Waterloo → Chicago → St Louis
Timetable, Chicago time
17:24AA 6365 from Waterloo at the gate
15:20UA 5901 to St Louis leaves the gate
21 h 56 apart on the timetable, overnight
UA 5901 leaves 21 h 56 after AA 6365 arrives on the timetable: more than half a day, so not a connection we count.