Air Canada is not bound by a contractual relationship. In 1988, the government passed legislation to privatize Air Canada. Parliament was the one that decided to privatize Air Canada, so it has the power to take over the company. Again, Parliament is sovereign and it can pass any laws it wants. At the moment, since the relationship is not contractual, we cannot talk about a breach of contract.
On June 8th, 2017. See this statement in context.