Originally Posted by
jackal
An MVP can book a ticket in the Y, S, or H class (Full Flex or the top couple fare classes in the Value category) and--if U is available--instantly confirm to First Class.
There are a lot of fare classes and it does get confusing. The MVP instant-upgrade classes are actually Y/S/B.
If you're buying your own ticket on alaskaair.com, they do make it relatively easy to choose your upgrade instrument/method and identify qualifying fares without having to deal with specific fare classes. You only really need to know fare class details if you are booking elsewhere.