As well as several other OneWorld and SkyTeam carriers, but seems to have an allergic reaction to Star Alliance members.
As such, I wouldn't be surprised to see UA take them out of the action... kill two birds with one stone; this would cripple both AA and DL on the west coast in a single blow. DL's PDX-NRT and AA's LAX-PVG would probably not be sustainable in the absence of AS feeds.