@chacko: I see. However I was not given an instant upgrade choice. There was no message, nothing. I just happened to notice it in the flight details before paying for the ticket. I could have very well bought the ticket without noticing and have turned up at the airport without knowing I had a business seat class (btw Austrian doesn't seen to have a first class section).

@flood: business was full. I didn't check Economy (I didn't want to be reminded that it existed!).