Not 100% sure, but not sure the EWR-YVR non-stop went this summer on UA. Also not sure on the AC specifics, but believe they were running 787s for a while on EWR-YVR. Not sure if they still are, or whether that was more about demand (IMO, probably not likely) or more about using them for training as they get more coming online. My guess: If AC continues to run 787s in the summer, you may not see UA running their own flight...given they are close partners, and it is probably more than enough demand.