AA 1991 then UA 5201 at O'Hare
Salt Lake City → Chicago → Milwaukee
Timetable, Chicago time
16:05AA 1991 from Salt Lake City at the gate
20:00UA 5201 to Milwaukee leaves the gate
3 h 55 apart on the timetable
The last days
AA 1991 and UA 5201 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.