BA 349 then UA 4 at Heathrow
Nice → London → Houston
Timetable, London time
21:05BA 349 from Nice at the gate
12:05UA 4 to Houston leaves the gate
15 h apart on the timetable, overnight
UA 4 leaves 15 h after BA 349 arrives on the timetable: more than half a day, so not a connection we count.