BA 349 then UA 925 at Heathrow
Nice → London → Washington
Timetable, London time
21:05BA 349 from Nice at the gate
16:20UA 925 to Washington leaves the gate
19 h 15 apart on the timetable, overnight
UA 925 leaves 19 h 15 after BA 349 arrives on the timetable: more than half a day, so not a connection we count.