AA 642 then UA 3909 at O'Hare
Dallas-Fort Worth → Chicago → San Francisco
Timetable, Chicago time
13:10AA 642 from Dallas-Fort Worth at the gate
19:30UA 3909 to San Francisco leaves the gate
6 h 20 apart on the timetable
The last days
AA 642 and UA 3909 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.