AA 3657 then UA 3910 at O'Hare
Key West → Chicago → Newark
Timetable, Chicago time
16:00AA 3657 from Key West at the gate
07:30UA 3910 to Newark leaves the gate
15 h 30 apart on the timetable, overnight
UA 3910 leaves 15 h 30 after AA 3657 arrives on the timetable: more than half a day, so not a connection we count.