DL 514 then AA 3978 at Phoenix
Boston → Phoenix → Denver
Timetable, Phoenix time
21:53DL 514 from Boston at the gate
15:15AA 3978 to Denver leaves the gate
17 h 22 apart on the timetable, overnight
AA 3978 leaves 17 h 22 after DL 514 arrives on the timetable: more than half a day, so not a connection we count.