Originally Posted by
gengar
To be clear, there's only one member who has ever claimed that "I" inventory guarantees SAUA availability. All the other data points (from 9 FT members) suggest that it is more likely "Z" inventory. Sorry that you got burned out of $50.
If you can verify that for the flight you could not upgrade, that Z=0, that would provide more clarity.
Not to unduly discount the data point provided by the other member, but going by the number of members who have success with checking Z rather than I availability (9 vs 1), we can at least say that checking Z is a much better bet than I, even if neither are a 100% guarantee.