AA 2123 then UA 3376 at O'Hare
Los Angeles → Chicago → St Louis
Timetable, Chicago time
20:04AA 2123 from Los Angeles at the gate
11:00UA 3376 to St Louis leaves the gate
14 h 56 apart on the timetable, overnight
UA 3376 leaves 14 h 56 after AA 2123 arrives on the timetable: more than half a day, so not a connection we count.