Originally Posted by
justhere
Are you sure about that? Wouldn't it be class of service paid? If it was class flown then why don't you get additional miles when buying an economy ticket but flying in first on a complimentary upgrade?
For the second question, they can tell by the fare bucket (e.g., O class for a complimentary elite domestic F upgrade from a coach fare) that it wasn't a paid F fare and won't award a class of service bonus.
The risk seems to be that the fare class might change if, for instance, you sit in coach on a paid F fare on a different flight where first wasn't available, which is what I believe
gottigotti is referring to. In that case, the computer is likely to award miles on whatever fare class was used to seat you in the coach seat. Unfortunately I don't have a definitive answer to that. The correct answer might actually be to refund the difference between the coach and first fares rather than award additional elite-qualifying miles.