The ECJ told the EU Member States to open their skies to each other as well as to the US when it decided eight cases on aviation treaties on 5 November 2001. Summary of the legislative framework of EC rights and bilateral treaties and a look at two examples of conflict between tax treaties and EC law (a conflict between secondary EC law relating to capital gains on group reorganizations and the Spain-US treaty and a conflict between primary EC law on the freedom of establishment and the new UK-US treaty). Also a brief explanation of the duty of the Member States to remove incompatibilities and the remedies available.