Originally Posted by
azeckel
I don't think even SDC will erroneously book into Y any longer. There's still a random set of events that will allow IRROPS to book into Y, but even in those cases, IT glitches are few and far between. Mileage now posts base on "fare paid" as opposed to fare flown.
There are instances where a flight may have positive space for sale, but the system won't process a SDC. When I've encountered this, most agents will switch me to another flight, but it has required them to change the fare basis to force the SDC through. The new fare basis will be recognised as the "paid" fare on the account statement.
Fare basis ≠ the single letter under "class" on the boarding card.