BA 349 then DL 37 at Heathrow
Nice → London → Atlanta
Timetable, London time
21:05BA 349 from Nice at the gate
16:00DL 37 to Atlanta leaves the gate
18 h 55 apart on the timetable, overnight
DL 37 leaves 18 h 55 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.