AS 306 then UA 8172 at San Francisco
Los Angeles → San Francisco → Boston
Timetable, San Francisco time
08:25AS 306 from Los Angeles at the gatealso QR 2087, QR 2123, QR 2172, QR 2178, TN 2353, QR 3435, IB 7260
12:45UA 8172 to Boston leaves the gate
4 h 20 apart on the timetable
The last days
AS 306 and UA 8172 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.