Originally Posted by
roberto.triviani
As an example, if U space isn't available, and the premium over main cabin fare is $100, it seems the best practice I've read on this thread is that one should not buy that upgradable fare. However, I assume in this case we are risking the premium going higher than $100 quoted in this example. Is that right? Any experiences or best practices to share?
Correct, it's possible that the lower GGU fare classes might sell out, or the fares may be expire or refile at a higher (or lower!) price depending on the lead time.
Note that if the lowest available fare class is your status' instant upgrade, U is open, and it's just you or you+1 companion, it makes more sense to save the GGU and just take the instant upgrade. M or higher qualifies for a Class of Service bonus.