Upgrades from main to first
 

I’ve got about $270 airline fee credits on my Ritz card exp in a month or so. Unless something has changed upgrades that I pay for are credited, have been in the past. I’m not familiar, though, with how airlines do this. I think in the past it was offered after purchase to upgrade, that was easy. Does that still happen on a regular basis? I’d book main, look at the difference with first and be willing to pay that difference. Doable online? I’d look at the big three and Alaska to do this. The latter seems to offer good deals upgrading but only last minute I think. Little guidance please, thank you.