At the Chicago Conference, the drafters of the Convention on International Civil Aviation had anticipated the emergence of a United Nations type of post-war organization. Accordingly, they wrote into the Convention a provision covering the possibility of ICAO becoming a constituent of such organization as follows:
The Organization may, with respect to air matters within its competence directly affecting world security, by vote of the Assembly, enter into appropriate arrangements with any general organization set up by the nations of the world to preserve peace.
At the first ICAO Assembly, held in May 1947, Resolution A1-2 was adopted by unanimous vote of the 32 Contracting States represented at the 3rd Plenary Meeting. This approved the agreement of relationship with the United Nations (UN) and authorized the President of the Council to sign a protocol bringing into force the agreement concerning such a relationship between the UN and ICAO.
ICAO became a UN specialized agency when President Edward Warner of the United States signed the protocol on 3 October 1947.
While ICAO remained an independent and autonomous agency after its UN system affiliation was formalized, its newfound UN status greatly benefited many of its Contracting States in the years which followed, for example through the United Nations Programme of Technical Assistance.
As a Specialized Agency of the UN, ICAO works closely with the Economic and Social Council, and has been prominently included in several Security Council meetings focused on global terrorism threats and terrorist international mobility more generally.
- The International Telecommunications Union (ITU);
- The International Atomic Energy Agency (IAEA);
- The International Labour Organization (ILO);
- The International Maritime Organization (IMO);
- The Universal Postal Union (UPU);
- The World Meteorological Organization (WMO);
- The World Health Organization (WHO); and
- The World Tourism Organization (UNWTO).