A bilateral aviation security agreement (BASA), a Memorandum of Understanding or Working Agreement (AV) and related implementation procedures provide for technical cooperation between national civil aviation authorities. They help to reduce duplication and aim at mutual recognition of certificates. In addition to airworthiness certification, bilateral aviation security agreements offer bilateral cooperation in a wide range of areas, including maintenance, air operations and environmental certification. With regard to aircraft certification, an additional document, an airworthiness implementation process, is being developed on certain areas, such as design approvals, production activities, export airworthiness authorization, design and technical cooperation. One of the first AAS after World War II was the Bermuda Agreement, signed in 1946 by the United Kingdom and the United States. The characteristics of this agreement have become models for the thousands of agreements that were to follow, although in recent decades some of the traditional clauses of these agreements have been amended (or “liberalized”) in accordance with the “open skies” policy of some governments, particularly the United States.  A horizontal agreement is an international agreement negotiated by the European Commission on behalf of EU Member States to bring into compliance with EU law all existing bilateral air services agreements between EU Member States and a given third country. Some traditions of international air transport regulation dating back to 1944 were contrary to the principles of the internal aviation market in Europe. While traditionally any international airline should have a particular nationality, the EU has developed a single market in recent decades in which eu member states can invest, create and control licensed airlines in another EU Member State. The term `EU carriers` has been reinforced by the fact that airlines are established and registered in the EU under the same rules and can serve any line within the EU. High standards are maintained and improved by common rules on key issues such as licensing, safety and security. In addition, certain aspects dealt with in the bilateral Air Services Agreements (ASA) fall under the exclusive competence of the EU and are therefore not self-negotiable by EU Member States. If an agreement does not contain the EU designation clause (all EU air carriers based in the territory of the EU Member State concerned have the opportunity to apply for available traffic rights), this would be contrary to the objectives of this common policy.