Originally Posted by
sodaisei
My question is, seats are offered in check-in counter? Not at on-line check in 24 hours before boarding?
Depends on the load. Sometimes you get the proactive upgrade by t-24 check in, otherwise it is checking your luck at the counter.
The plane will not fly (usually) with a Diamond in economy class and an empty premium economy seat. You might even get a last minute upgrade at the gate.