AA 818 then UA 3872 at O'Hare
Charlotte → Chicago → LCQ
Timetable, Chicago time
12:22AA 818 from Charlotte at the gate
00:31UA 3872 to LCQ leaves the gate
12 h 09 apart on the timetable, overnight
UA 3872 leaves 12 h 09 after AA 818 arrives on the timetable: more than half a day, so not a connection we count.