So this question may have already been asked.
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I am looking at the Delta Reserve because I want Skyclub Access and was looking around at the annual companion certificate and I don't fully understand how it works.

Deltas website states that it allows a companion to travel with me on an "eligible round-trip domestic flight".

How does Delta define eligible? Are all Delta Mainline and Delta Connection flights fair game or are there blackouts? It says in the terms and conditions that it's for a main cabin seat. So if I book a flight for myself and use my certificate for my fiancee, and I get bumped to first or C+ for being a PM, will she still be upgraded like if I bought a normal ticket on my reservation?

I'm just wanting to make sure this benefit works as I hope because if it does, that will be one of the deciding factors for me if I want to drop the $550 on this card. Since AmEx decided to make the Plat $700, that option is now way off the table for me.