Originally Posted by
roadtripman
It looks like they're only using certain airlines. The cheapies seem to be excluded. I've tried to book Calgary - Vancouver, and its putting me on expensive Air Canada, and not cheapy Westjet, resulting in the ticket being around $300 more than it should be

I have never noticed WestJet to be anything close to a "cheapie". They always match Air Canada's fares and vice versa.