UA 3873 then AA 4963 at O'Hare
Fort Worth → Chicago → Milwaukee
Timetable, Chicago time
17:55UA 3873 from Fort Worth at the gate
06:49AA 4963 to Milwaukee leaves the gate
12 h 54 apart on the timetable, overnight
AA 4963 leaves 12 h 54 after UA 3873 arrives on the timetable: more than half a day, so not a connection we count.