But there's a difference in power. Air Canada doesn't have the same power over Canadian citizens that the United States may have over Canadians who find themselves in the U.S., or flying over it, or even being extradited. Air Canada doesn't have that power.
But to answer your question, I think it would be an excellent idea. I think transparency is always the best approach in dealing with people's personal information. I would favour telling them when they purchase tickets that these elements of information are going to be disclosed to such and such country that they will be overflying. For the moment, it's only the United States.