AA 1509 then UA 521 at Atlanta
Cleveland → Atlanta → Houston
Timetable, Atlanta time
09:08AA 1509 from Cleveland at the gate
15:57UA 521 to Houston leaves the gate
6 h 49 apart on the timetable
The last days
AA 1509 and UA 521 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.