My fiance and I are flying to bangkok with Austrian on our honeymoon in August. They have said we may have the option to purchase an upgrade to Business Class but only when our online check in opens 36 hours before our flight. I really want to do this but have no idea of roughly how much it will cost. We would only want to do it on the way out from Vienna. I have emailed them asking for a cost estimate and they said they cannot tell me. Has anyone else done this? Our ticket class is L. Many thanks.