Originally Posted by
armagebedar
Essentially all fares are upgradeable to Premium Class by paying the same-day, space-available upgrade fee.
Because availability changes from moment to moment. On trunk routes especially, most Premium Class fares are changeable without fees so availability fluctuates right up until departure.
Weird, because right before check in I was looking at expertflyer which showed F4 and 6 empty seats.
I asked the agent, and she said F is full. I then took my bag, walked up to the Premium Class check-in, asked if I could upgrade and the ticket agent said ok and wrote down the price for me.
I started to think maybe not all check-in counters/agents are the same.