A friend of mine said that if I take a flight, I will need a statement written by a doctor that my migraine medicines (Pronaxen) are legal. Is that true? I have had flight around the Europe, like Helsinki, Riga, Copenhagen, Lisbon, Barcelona, but this question popped to my mind only now. How can a doctor make sure that I won't remove the medicine and put something illegal to the pot after he or she has been written the statement?