AC 523 then AA 2444 at O'Hare
Montréal → Chicago → St Louis
Timetable, Chicago time
15:00AC 523 from Montréal at the gate
20:18AA 2444 to St Louis leaves the gate
5 h 18 apart on the timetable
The last days
AC 523 and AA 2444 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.