AA 4509 then UA 4535 at O'Hare
Knoxville → Chicago → Pittsburgh
Timetable, Chicago time
09:10AA 4509 from Knoxville at the gate
12:48UA 4535 to Pittsburgh leaves the gate
3 h 38 apart on the timetable
The last days
AA 4509 and UA 4535 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.