Originally Posted by ibling

Regardless of whether you book directly into W class or upgrade to it, AS will credit based on the fare code which it books into. All Delta W class fares are actually booked into Main Cabin fare class underneath, and so credited by AS accordingly.

If anyone is interested, I have highlighted this with an example and snapshots in my recent blog post - http://travelupdate.boardingarea.com...rt-plus-class/