I spent a long time on the phone with Air Canada earlier this week, and had a bit of a discussion with the res agent about their whole situation. She told me that their feeling is that they should be quite safe, her reasoning is this:
Apparently the bigwigs in the Federal government get free seats on Air Canada. If they let it go under, then they have to pay for their tickets.
And despite the fact that it makes news frequently up here, it's not that much of a concern in the US. Virtually all their big airlines are in much worse shape financially than Air Canada is. Delta's debt is several times what AC's is.
Worry more about United - their codeshare partner for the US side. United is trying to file for bankruptcy protection, again.