AM 686 then AA 3484 at O'Hare
Mexico City → Chicago → St Louis
Timetable, Chicago time
13:12AM 686 from Mexico City at the gate
09:30AA 3484 to St Louis leaves the gate
20 h 18 apart on the timetable, overnight
AA 3484 leaves 20 h 18 after AM 686 arrives on the timetable: more than half a day, so not a connection we count.