AA 1991 then WN 1737 at Salt Lake City
Chicago O'Hare → Salt Lake City → Denver
Timetable, Salt Lake City time
10:58AA 1991 from Chicago O'Hare at the gate
15:10WN 1737 to Denver leaves the gate
4 h 12 apart on the timetable
The last days
AA 1991 and WN 1737 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.