Don't underestimate the value of an impressive-looking route map that covers the entire planet, while maintaining a fleet that's 30 times smaller than would be required to physically fly those routes.
Ah, gimmickry! I knew it!
There are lots of other benefits too, including getting to keep fuel surcharges, based on the marketing flight numbers.
If AC looses 1 grandmother and gains 10 other PAX, based on their ability to market and sell non-existent AC flights, do you think it would be a tough choice to make?
Well, yeah, you're right -- it does allow more visibility in the reservations system. Instead of just 2 or 3 AC-operated flights showing on a route like YYZ-LAX, there's maybe a dozen that show up, compared to, Westjet's 1 or 2 that get drowned out.
But, on the other hand, doesn't the existence of 15 flights sort of create the perception of competition that really doesn't exist? UA might drop their price on the YYZ-LAX codeshare by $10, and suck sales away from AC. When half a dozen codeshares on the same route, on the same physical aircraft, isn't there almost certainly always at least one of the codeshare partners who offers the flight less expensively than the others? Would this not exert a downward force on pricing overall?
I know that, when I'm out shopping for goods and services, if 7 places are offering the same service, I can approach each of them and attempt to negotiate a lower price, ie: I get 7 'kicks at the can'. Whereas, if the service is only offered by 1 operator, there's not much ability to negotiate, eh?