UA 3874 then AA 4441 at O'Hare
Chicago → Chicago → Madison
Timetable, Chicago time
01:21UA 3874 from Chicago at the gate
17:16AA 4441 to Madison leaves the gate
15 h 55 apart on the timetable
AA 4441 leaves 15 h 55 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.