B6 778 then AA 4357 at Boston
Las Vegas → Boston → New York JFK
Timetable, Boston time
06:32B6 778 from Las Vegas at the gate
06:00AA 4357 to New York JFK leaves the gate
23 h 28 apart on the timetable, overnight
AA 4357 leaves 23 h 28 after B6 778 arrives on the timetable: more than half a day, so not a connection we count.