AA 434 then WN 1590 at Boston
Miami → Boston → Denver
Timetable, Boston time
10:20AA 434 from Miami at the gate
16:40WN 1590 to Denver leaves the gate
6 h 20 apart on the timetable
The last days
AA 434 and WN 1590 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.