I think I know which airline you are on about, this would be the one who don't put seat numbers on boarding cards, but board you by security/check-in number, let you pick your seat.
Hmmm not the best of descriptions to identify a particular low-cost carrier as there are several based at STN that do not allocate seats.
Still, at least I can say that it is NOT easyJet as we do not fly to Austria
