AA 1813 then UA 3876 at O'Hare
Portland (Oregon) → Chicago → Miami
Timetable, Chicago time
05:07AA 1813 from Portland (Oregon) at the gate
21:00UA 3876 to Miami leaves the gate
15 h 53 apart on the timetable
UA 3876 leaves 15 h 53 after AA 1813 arrives on the timetable: more than half a day, so not a connection we count.