Appears AS passengers have baggage rules enforced ... when they fly AA.

I was flying a codeshare on AA (LAX-DEN) a week ago. When I began to board, the previously smiling GA looked at my boarding pass, made a comment about it stating I'm an Alaska Airlines frequent flier, then told me to put my bag in the sizer. Which took me out of the boarding queue and to the other side of the podium.

It's a standard 22" TravelPro roll-aboard that fit easily, and has fit easily in every 737-800 aircraft I've ever flown -- which is what I was flying that day.

I was the only passenger asked to do so before I boarded, and it only came after the AS comment by the GA. Great relationship between "partners" there.