AA 2166 then UA 3872 at O'Hare
Boston → Chicago → LCQ
Timetable, Chicago time
12:29AA 2166 from Boston at the gate
00:31UA 3872 to LCQ leaves the gate
12 h 02 apart on the timetable, overnight
UA 3872 leaves 12 h 02 after AA 2166 arrives on the timetable: more than half a day, so not a connection we count.