zrs70

I'm still trying to navigate the DL elite system, so pardon my ignorance ...

If a flight search shows upgrade eligible, I understand this means that the fare is eligible for an upgrade, and if it becomes available closer to flight time I might get something.

If, at the time of booking, it shows upgrade available, does that mean that the upgrade should clear upon purchase? Is the upgrade available only with certain fare buckets?

What if I have a ticket that is already purchased (a month ago) and I am on the waitlisted for first... Now, when I look online, that segment shows upgrade available. Should Delta be able to clear me?

What if I have a ticket that is a P, Z, or D fare, but one of the segments is in coach because it's a one cabin aircraft. What if there is a schedule change and that segment becomes it two cabin aircraft?

One final question… Is there a way to see upgrade availability with miles or upgrade certificates for long-haul or business one flights?

Thanks and advance!