Montréal-Trudeau moves more than twenty million passengers a year, and the difference between a calm departure and a stressful one is almost always timing. For domestic flights, plan to be curbside two hours before departure; for transborder and international, three. In January and February, add a further thirty minutes for de-icing queues and highway conditions.
Arrivals work differently. Curbside pickup is faster and cheaper, but if you are travelling with children, heavy luggage or a client you have never met, the inside greeter service pays for itself. Your chauffeur waits at the baggage claim exit with a name board and walks you to the vehicle.
Always give your airline and flight number when booking rather than only a landing time. Flight tracking lets dispatch shift your chauffeur automatically when the aircraft moves, which is the single most common cause of missed connections between passenger and car.
Finally, confirm the meeting point in writing. YUL has multiple arrival doors and a busy departures ramp, and a one-line confirmation of exactly where to stand removes the only real friction point in an otherwise simple transfer.

