FR 3977 then UA 770 at Barcelona
Dublin → Barcelona → Chicago
Timetable, Barcelona time
21:10FR 3977 from Dublin at the gate
15:10UA 770 to Chicago leaves the gatealso AC 4575, LH 8858
18 h apart on the timetable, overnight
UA 770 leaves 18 h after FR 3977 arrives on the timetable: more than half a day, so not a connection we count.