AA 706 then UA 3907 at O'Hare
Washington National → Chicago → Washington
Timetable, Chicago time
16:18AA 706 from Washington National at the gate
12:00UA 3907 to Washington leaves the gate
19 h 42 apart on the timetable, overnight
UA 3907 leaves 19 h 42 after AA 706 arrives on the timetable: more than half a day, so not a connection we count.