AA 2436 then UA 3376 at O'Hare
San Francisco → Chicago → St Louis
Timetable, Chicago time
15:15AA 2436 from San Francisco at the gate
11:00UA 3376 to St Louis leaves the gate
19 h 45 apart on the timetable, overnight
UA 3376 leaves 19 h 45 after AA 2436 arrives on the timetable: more than half a day, so not a connection we count.