Originally Posted by 2035

Doesn't always work. Once at TLV I saw a big stack of F boarding passes at the podium for op-ups - SENS and FTLs mostly. I didn't get one. The C cabin was completely full - no seat blocking. I kicked up a fuss, and they tried to tell me there were no op-ups. Eventually they downgraded a non-revenue pax (ie frieds of the pilot) to C and gave me his seat.
Another time, after promising me at check-in that KSML doesn't stop the upgrade, they upgraded all SENs to F, and didn't give me one. They wouldn't give me an op-up, and told me I was delaying the flight.
So it doesn't always help...but often does! I think they have to manually override the system suggestions for op-ups, which they sometimes forget to do.