BA 391 then DL 37 at Heathrow
Brussels → London → Atlanta
Timetable, London time
16:20BA 391 from Brussels at the gate
16:00DL 37 to Atlanta leaves the gate
23 h 40 apart on the timetable, overnight
DL 37 leaves 23 h 40 after BA 391 arrives on the timetable: more than half a day, so not a connection we count.