I feel like a fish out of water asking what could be such a n00bish question, but I've never done this before....
My friend and his wife are flying TLV-EWR on UA, in W class. I seem to recall hearing from someone that people sometimes sell "upgrades" for a few hundred bucks, on FT or craigslist or whatever. I have no idea how this works (GPU? RPU? Something else?)
Questions:
1) What is the official name for this upgrade? Does it work for TLV-EWR?
2) If yes, will it work for W class? And if W class is not good enough, is there a "co-pay" option like there is when upgrading with miles, and how much money?
3) Anything else I should know?
TIA!