AA 3258 then UA 3902 at Houston
Miami → Houston → Washington
Timetable, Houston time
09:00AA 3258 from Miami at the gate
12:30UA 3902 to Washington leaves the gate
3 h 30 apart on the timetable
The last days
AA 3258 and UA 3902 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.