DL 348 then UA 1254 at Atlanta
Phoenix → Atlanta → Denver
Timetable, Atlanta time
17:15DL 348 from Phoenix at the gate
11:14UA 1254 to Denver leaves the gate
17 h 59 apart on the timetable, overnight
UA 1254 leaves 17 h 59 after DL 348 arrives on the timetable: more than half a day, so not a connection we count.