Originally Posted by
lsumegan
That the fare class you need is not available even though there are empty seats, so you can not SDC. You can SDS but probably will not get an upgrade.
This and the fact that due to the fare class availability, if you've purchased a G A P fare, not only can you not SDC, but when you SDS you will almost always end up sitting in coach even though you purchased a FC fare and other elites have been upgraded at the gate.