The Plenipotentiary Conference held in Montreux in 1965 marked the Centenary of the Union. The Conference introduced several changes in the structure of the Union: the Administrative Council was enlarged from 25 to 29 members, and the membership of the IFRB was reduced to 5 instead of 11.

The development of satellite communications as well as the creation of regional telecommunication unions to solve problems of a regional nature obliged the ITU to reorganize its Administrative Conferences so as to be able to deal separately with international and regional questions. The Conference decided to define 2 types of Administrative Conferences:

- World Administrative Conferences to deal with telecommunication questions of a worldwide character concerning all types of telecommunication services (telegraphy, telephony, radiocommunications, broadcasting, space communications, maritime and aeronautical services, etc.)

- Regional Administrative Conferences to deal with problems of a regional nature; the subject may concern either a given geographical region or a specific telecommunication service of a regional nature. The decisions of these Conferences should be in conformity with the Regulations of the World Administrative Conferences and not conflict with the interests of other regions