That's if you believe the fairy tale that's called cabotage. The fact of the matter is, cabotage by definition cannot exist, as it existing would mean that you would be able to prove the intent of the passenger. For instance, flying Toronto to Vancouver via Denver on United could be seen as cabotage to some. But what if you are flying into Denver in the morning, having a meeting there then flying in the evening to Vancouver? By definition, this ain't cabotage. Even a short layover like 1-2 hours at an airport in the US may not be seen as cabotage since again you might be meeting a colleague at the airport before flying onwards.
Indeed, Air Canada will happily sell you such a ticket:
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