Recently I was looking at a flight from Boston to Los Angeles, and one particular flight suggested was interesting - connecting through Toronto (airlines were Air Canada and WestJet). Due to the hassle of crossing an international border I am not going to be booking this flight, but I am curious about how customs/immigration work in this case? Would I need to clear customs when landing in Toronto, then reclear US immigration at Toronto?

2 Answers 2


Yep, you'd have to clear two sets of customs and immigration in Toronto. I'd initially assumed they'd have some program to let connecting passengers from the US directly into the post-preclearance terminal area, but https://www.torontopearson.com/connecting.aspx suggests that's not an option (possibly because of the airline/terminal change).

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    From a pure mercantilistic perspective there wouldn't be much reason for US authorities to cooperate with such an arrangement as part of their preclearance presence. Their goal is to make it easier for outsiders to come to the US for business or tourism purposes (both presumably profitable for the US as a country), not to give Canadian airlines a way to compete for the US domestic market. Mar 11, 2019 at 13:53
  • @HenningMakholm How does preclearance make it easier for outsiders to enter the US? It makes it quicker to get out of the airport after landing, of course, but only at the expense of having to allow more time at the departure airport before boarding.
    – phoog
    Mar 11, 2019 at 17:02
  • @phoog: For example, from time to time we advise people who are unsure of their admissibility to fly from an airport with preclearance, because being rejected there is a lot less invasive than being rejected at the destination. That's at least easier for a particular group of travelers, namely those worried about being admitted or not. I'd also say it is easier even for people who are fairly sure they'll be admitted, if they have a transfer to a domestic flight when they arrive. If you're precleared, your connection will not be in jeopardy by unpredictable immigration queues. Mar 11, 2019 at 17:23

This is a form of international air travel called "cabotage" which is not allowed under most bilateral air transportation treaties, including the agreement between the US and Canada. You are not allowed to transit Canada on a domestic US itinerary unless the stop is longer than 4 hours, at which point your Canadian connection is defined as a stopover, as opposed to a layover. Neither the Westjet nor Air Canada websites should sell you a ticket with a shorter layover, and if you piece together an itinerary like that on your own you will likely be denied boarding at the airport.

That being said, if you were to book this ticket and it did meet the four hour minimum requirement, yes you would have to clear customs twice at YYZ, once to enter Canada and once to reenter the US.

Here are a few resources:

Discussion of Canadian Cabotage from Flyertalk

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    That's surprising. Are you saying Air Canada is supposed to deny you boarding if they find out you have a separate WestJet ticket you plan to use right afterwards?
    – Sneftel
    Mar 11, 2019 at 15:57
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    They're supposed to, though in practice it's unlikely that they'll catch you. What's more likely to happen, I suppose, is that you'll get in trouble with Canadian CBP, though as that point I'm not sure whether they would try to send you back the way your came or let you continue.
    – cbw
    Mar 11, 2019 at 15:59
  • The link you have called "Cornell Law Definition of Cabotage" is published on the web by the Cornell Legal Information Institute, but it is not attributable to them; it is a US government customs regulation from the Code of Federal Regulations. It does not directly concern international agreements, but rather unilateral US legal restrictions on using foreign aircraft for transportation between points in the US. This regulation does not even touch on the question of whether transportation between points in the US by way of a point outside the US (the issue here) falls within its scope.
    – phoog
    Mar 11, 2019 at 17:12
  • @phoog Fair enough. It was meant only as a definition of cabotage, nothing more. I've removed it
    – cbw
    Mar 11, 2019 at 18:57
  • A passenger cannot break cabotage laws, only an airline can. Thus airlines don't care if you have a separate ticket, as long as you didn't book it on one itinerary, especially if different airlines are involved.
    – JonathanReez
    Mar 11, 2019 at 20:52

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