UA 374 then AC 1557 at Newark
Phoenix → New York → Montréal
Timetable, New York time
05:58UA 374 from Phoenix at the gate
10:20AC 1557 to Montréal leaves the gate
4 h 22 apart on the timetable
The last days
UA 374 and AC 1557 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.