The agreement consists of a number of principles of general application and specific commitments in the areas. Certain general principles of the GATS govern the process of progressive liberalization, which takes place through specific commitments by Member States in cyclical negotiations, described in detail in Chapter IV. In addition to the rules on specific commitments in the areas, the GATS also contains general rules in force since the end of the Uruguay Round. These include the most-favoured-nation clause in Article II, transparency obligations (Article III), certain disciplines on rules of procedure and bilateral mutual recognition agreements. Some annexes to the GATS set out specific rules for certain sectors such as air transport, telecommunications, financial services and natural persons. Generally speaking, each of these agreements has led Member States to reduce customs duties on trade (but with many exceptions from time to time, both for certain products and for certain countries). Finally, a second type of derogation from the application of the GATS framework concerns a particular area: air services. In accordance with the Annex on Air Services, the GATS does not apply to regulatory measures relating to air navigation rights and services directly related to the exercise of those rights. The task of the Trade in Services Council is to monitor developments in the air transport sector and to decide, at least every five years, on the possibilities for the full application of the GATS framework. In 2003, the Council decided not to amend the GATS exception for air transport. .