UA 3874 then AA 2499 at O'Hare
Chicago Rockford → Chicago → Dallas-Fort Worth
Timetable, Chicago time
01:21UA 3874 from Chicago Rockford at the gate
17:16AA 2499 to Dallas-Fort Worth leaves the gate
15 h 55 apart on the timetable
AA 2499 leaves 15 h 55 after UA 3874 arrives on the timetable: more than half a day, so not a connection we count.