My first 25k USAir preferred miles were on Air Canada earlier this year. It's much more convenient to fly AC when you're in PHX and need to get to YYZ (Toronto). I've never earned bonus miles, but I always get the preferred. AC is actually a really nice airline to fly with. All of their plans have personal TVs and they have current movies. Plus, the boarding process is so much more pleasant as there is no mad rush to get on the plane.