UA 728 then AA 1408 at DFW
Denver → Dallas-Fort Worth → Huatulco
Timetable, Dallas-Fort Worth time
16:39UA 728 from Denver at the gate
10:49AA 1408 to Huatulco leaves the gate
18 h 10 apart on the timetable, overnight
AA 1408 leaves 18 h 10 after UA 728 arrives on the timetable: more than half a day, so not a connection we count.