Now, read this:
In December, travelling to Europe (final destination: Vienna), I bought perfumes on-board duty free of Air France flight to Paris.
Everything was good, until I got to Paris to take my connecting flight to Vienna. Paris airport is so badly designed, that for EVERY connecting flight regardless if you go through customs or not, you have to clear security again. Frankfurt or Munich is much better for this point.
So now my carry-on bag with 6 perfumes gets flagged!! There is no way to put that into your checked bag in Paris, because in EU bags are checked and cleared to final destination, regardless of where you enter the Schengen zone. (In other words, you do not pick up your bags in Paris upon entering the EU, as is the case in the USA, but rather in your final destination, in this case, Vienna).
The security didn't want to let me board the plane, because, supposedly, the duty-free bag was supposed to be SEALED on board the flight, and that way could be taken past security. It took me some begging and showing purchase receipt, and "it's Christmas" please to let me through.
So at least in the USA, you have a way to put it in your bag when you get your bags cleared through customs at your first point of entry. Flying to Europe is a different thing and you should think of this!
So if you purchase something ON-BOARD the flight, get it sealed! With the airline seal! And if they don't have seals, demand that a report be written and carry it with you, and then talk to supervisors to let you board connecting flight, or make them deliver it to your final destination somehow.
The seals do not work for airport duty free purchases going into connecting flights, only for seals given on EU carriers heading to the EU airport.