OO 9921 then UA 5752 at O'Hare
Phoenix → Chicago → Detroit
Timetable, Chicago time
15:57OO 9921 from Phoenix at the gate
19:47UA 5752 to Detroit leaves the gate
3 h 50 apart on the timetable
The last days
OO 9921 and UA 5752 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.