Originally Posted by
JALPak
If there's no paid F passenger, it may be more cost effective to just use the F cabin as C instead. When you say 5-15 seats left in C, did you use the seat map? That is not an accurate indicator of availability in the cabin.
I looked at making another booking in addition to my existing reservation, and I checked the symbol that appeared (I believe it was a white triangle) against the key, which indicated 5-15 seats.