UA 1603 then AA 939 at San Francisco
Las Vegas → San Francisco → Dallas-Fort Worth
Timetable, San Francisco time
19:03UA 1603 from Las Vegas at the gatealso AC 3072, LX 3126
23:23AA 939 to Dallas-Fort Worth leaves the gatealso CZ 1632
4 h 20 apart on the timetable
The last days
UA 1603 and AA 939 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.