AA 4639 then AF 2818 at JFK
Boston → New York → San Francisco
Timetable, New York time
07:29AA 4639 from Boston at the gate
19:30AF 2818 to San Francisco leaves the gate
12 h 01 apart on the timetable
AF 2818 leaves 12 h 01 after AA 4639 arrives on the timetable: more than half a day, so not a connection we count.