Originally Posted by tvnwz:18617661
I think you should have been allowed to keep your seat. And this from a DM to the lowly FO

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Once you have the boarding pass, it becomes your seat IMHO.
I would've thought the same thing. By ec, delta explicitly writes that they can change your seat at their discretion, but it doesn't say that by first. Once you get the confirmed upgrade, it should be yours and they shouldn't be allowed to mess with it