UA 4500 then UA 992 at Dulles
Detroit → Washington → Barcelona
Timetable, Washington time
21:17UA 4500 from Detroit at the gate
18:50UA 992 to Barcelona leaves the gate
21 h 33 apart on the timetable, overnight
UA 992 leaves 21 h 33 after UA 4500 arrives on the timetable: more than half a day, so not a connection we count.