[QUOTE=FCfree;9157217]
Northwest and Continental are the best on this -- giving FREE, UNLIMITED first class upgrades, space available, once you become SILVER or better.

I guess the qualifier "space available" would cover the instance where NWA simply did not OFFER any first class style seats or service on the plane--as is the case with some of their transpacs--if not all, I believe.

But I bet by now the OP has "gotten the message"-- and a pretty consistent answer to her question.