You raise a good point about the F vs. C. I have some murky recollection about SFO-MEX tickets upgrading into NC rather than NF even though it's a two class aircraft (320). A CSR explained that it was due to the "international flight". Any of you heard this?

This matters in terms of checking for X (NF) vs. I (NC) class inventory before booking...

Any consensus on what I should be looking for here?