UA 2138 then AA 6279 at O'Hare
St Louis → Chicago → Kalamazoo
Timetable, Chicago time
14:35UA 2138 from St Louis at the gate
14:18AA 6279 to Kalamazoo leaves the gate
23 h 43 apart on the timetable, overnight
AA 6279 leaves 23 h 43 after UA 2138 arrives on the timetable: more than half a day, so not a connection we count.