UA 818 then UA 728 at Houston
Buenos Aires → Houston → Denver
Timetable, Houston time
05:20UA 818 from Buenos Aires at the gate
08:30UA 728 to Denver leaves the gate
3 h 10 apart on the timetable
The last days
UA 818 and UA 728 weren’t both flown 15 min to 12 h apart in the last 21 days.
Statistics from past flights, not live flight information. Always check times and your connection with your airline, and don’t base travel or booking decisions on these numbers.