The article first analyses the relationship between the Montreal Convention and Regulation 261/2004. Although the Regulation and the Convention both relate to the protection of air passenger’s rights it remains ambiguous when and in which disputes these acts should be applicable. Thus, this article reveals the problematical issue of how these acts differ and in which situations they are applicable. Second, it reviews the development of the EUCJ case law regarding the application of these acts. Third, it examines the relevant case law of the Supreme Court of the Republic of Lithuania in this area.