AA 2343 then UA 3376 at O'Hare
San Diego → Chicago → St Louis
Timetable, Chicago time
16:29AA 2343 from San Diego at the gate
11:00UA 3376 to St Louis leaves the gate
18 h 31 apart on the timetable, overnight
UA 3376 leaves 18 h 31 after AA 2343 arrives on the timetable: more than half a day, so not a connection we count.