Originally Posted by
exerda
On PMUA, anyway, the flight must be booked to no more than capacity - 1, in the same class of service.
This means there are cases where they may still be selling seats (as they're willing to overbook via sales), but you cannot do SDC.
About 10 days ago I tried to do a confirmed SDC and the agent said she was sorry, she couldn't do it as there was only one seat left and the flight had to be sold to at least -2 under capacity. I commented I thought as long as there was one seat you could get confirmed, but she indicated I was incorrect and it was -2.
It was SFO-LAX, and I was on my way to the airport when I called, so I just asked to be added to the wait list and cleared at the gate.
At any rate, as usual, YMMV.