Obviously, this can become problematic, because you are giving the keys to the kingdom to a single company, in this case a company that often sets itself apart, but not for the right reasons: it is the subject of several complaints, both in terms of language and services offered.
It also puts the entire industry at risk. Less competition means fewer players in the value chain for services, because you want to get volume discounts, and if there are fewer players, then fewer suppliers are engaged. But the value chain and the critical chain are important because if there are fewer suppliers, as soon as one of them has a problem, it can affect the whole industry. If there is a global computer failure, as we've already seen with some carriers, it affects the entire industry. If there is widespread piracy, it will affect the entire industry. Obviously, the less competition there is, the more the industry is at risk, and the less we try to stand out.
This is also the case for other stakeholders. I'm thinking of travel agents and travel agencies. If there isn't as much competition, these people won't have the choice to use a given supplier, then there will be no room for negotiation.
The same applies to passengers. If there isn't enough airline choice in Canada, and they are forced to choose between Air Canada and Air Canada, they risk going to an airline outside of Canada, which can result in a reduction in market share for Canadian companies.