Originally Posted by
ecgz88
2. Except departure from UK, when I upgrade in airport I just need pay the miles difference? or I still need pay tax/fees difference?
I don't know if it's still true, but when this was discussed a while back, the UK, Pakistan and Lebanon were the 3 places mentioned as having extra tax to pay.
https://www.flyertalk.com/forum/12171271-post2.html