I’m certain that United pilots can also “book” the jumpseat. I do it all the time. It is as you know awarded in seniority order with the Captain having the final say.

Are you saying that Delta’s policy is to remove the Captain’s authority? If so, how is that done within FARs?

I wouldn’t vote for any degradation of Captain’s authority. Further, I don’t think I’d support a degradation of “seniority order”.

This doesn’t appear to be in the agreement so it’s not really up for debate, but honestly I wouldn’t see that as a win. Certainly a conversation for next time.