Originally Posted by
FlightNurse
This is not true, it won't clear immediately. There might be seats available but that doesn't mean AA will upgrade quickly. Remember it goes by status first and granted you are Gold, there might be PLT or PP ahead on the upgrade list. In regards to the DFW = PHX fight, anything is possible but I highly doubt you will get an upgrade. It doesn't hurt to try on the upgrades.
I think you are the one in error - if C is available then upgrades will clear immediately (or at least as soon as you call in). If there were just seats available, but the flight was C0, then your argument would be more correct - but even then it is often the case that C is made available 12-48 hours before a flight, before X is made available and before it goes to gate control.
If you are not EXP and flying a popular route then Miles+ copay is probably the only way to snag an upgrade.