Originally Posted by
dera
Positive space means they will kick out a paying passenger to accommodate you. So that is why it is not PS. Oversales also have higher priority than A12, so they can (and will) sell a plane full even if you have a confirmed seat.
How often this happens, I have no personal experience so I can't comment on it. But it's possible.
maybe it’s possible, but every time it happened to me, I kept my seat, even on crazy days with lots of cancellations around the holidays.