AA 2343 then UA 5901 at O'Hare
San Diego → Chicago → St Louis
Timetable, Chicago time
16:30AA 2343 from San Diego at the gate
15:20UA 5901 to St Louis leaves the gate
22 h 50 apart on the timetable, overnight
UA 5901 leaves 22 h 50 after AA 2343 arrives on the timetable: more than half a day, so not a connection we count.