Annex 3 - Meteorological Service for International Air Navigation


Developed by ICAO, the International Standards and Recommended Practices (SARPS) contained in the nineteen Technical Annexes to the Convention on International Civil Aviation (also called Chicago Convention) are applied universally and produce a high degree of technical uniformity which has enabled international civil aviation to develop in a safe, orderly and efficient manner.


From the early days of aviation, it was realized that meteorological information was vital for the planning and a constant factor for the safe conduct of flights; pilots need to be informed about meteorological conditions along the routes to be flown and at their destination aerodromes. The high operating cost of modern aircraft means that optimum use must be made of available meteorological information and that forecasting accuracy must continue to be improved. The increasing use of flight management computers and the establishment on-board aircraft of reliable data links between aircraft and ground make it possible to monitor flight progress and update flight plans on the basis of new weather conditions. 


As the Organization preceding ICAO, the International Commission for Air Navigation (ICAN) held twenty-nine sessions between July 1922 and October 1946, with an interruption during WWII. ICAN had created its own Meteorological Commission and drafted Annex G, named Collection and dissemination of meteorological information, to the Convention for the Regulation of Aerial Navigation.

Annex 3 – Front page

The Convention on International Civil Aviation at Chicago had made provision for Annex I on Meteorological protection of international aeronautics. When PICAO came into existence in 1945, Technical Divisions composed of specialists from Members States and of observers from organizations interested in international civil aviation, assisted by the Organization’s Secretariat, were directed and coordinated by the two committees of the PICAO Council, i.e. the Air Navigation Committee and the Air Transport Committee. As standards were developed by ICAO, either the subjects of annexes were split or new annexes were conceived, and most of the titles were revised.

The Meteorology (MET) Division held 18 meetings between 11 October and 2 November 1945. The second session of MET Division was held from 29 October to 16 November 1946 to review the Recommendations for Standards, Practices and Procedures prepared during the first session. On 24 January 1947, the PICAO Council authorized the transmission of the Division's final report to Member States, for comments on the Recommendations for Standards, Practices and Procedures within 90 days of the date of despatch. Taking advantage of the presence in North America of meteorologists attending the meetings of the IMO Technical Commissions, the MET Division held on 17-18 September 1947 a special session to determine the desirable amendments to be brought to meteorological codes. Further to the latter session, the new Annex 3 titled Meteorological Codes was first adopted by the ICAO Council on 16 April 1948 providing the meteorological codes for the transmission of meteorological information for aeronautical information.

With the introduction of Standards and Recommended Practices governing the obligations of Contracting States relating to the establishment of meteorological organization in each State, a change of title of Annex 3 – Meteorology was adopted by the ICAO Council on 1 April 1955.


With a complete revision of Annex 3, incorporating PANS-MET specifications (Procedures for Air Navigation Services, Meteorology), taking into account recently approved operational requirements and up-to-date methods of meeting them and with the introduction of new Standards and Recommended Practices relating to service for operators and flight crew members, meteorological information for air traffic services and for search and rescue services, together with requirements for communications and their use, the title of Annex 3 was, accordingly, amended to read Meteorological Service for International Air Navigation and adopted by the Council on 26 November 1975.


ICAO has achieved especially significant progress in meteorological standards since the 1980s, with the implementation of two global initiatives: World Area Forecast System (WAFS) and the International Airways Volcano Watch (IAVW).


In November 1984, following the Communications/Meteorology Divisional Meeting that was held in 1982, new provisions related to the introduction of the world area forecast system (WAFS) were introduced in Annex 3 that assisted States in concentrating meteorological resources to improve forecasts for terminal areas, given the critical impact on safe and economic aircraft operations. Since their inception, the WAFS has been progressively improved through the introduction of updated SARPs in fourteen subsequent amendments to Annex 3. This has ensured the ongoing provision of high-quality, consistent and uniform forecasts for flight planning and aircraft operations. Recently, as recommended by the Conjoint ICAO-WMO Divisional Meeting that was held in Montréal in 2014, the WAFS is being further developed and improved to ensure that it is able to cope with future requirements due to changes in airline business perspectives, flight operations and routes and the increase of data volumes, and to meet developing System Wide Information Management (SWIM) demands.

To meet the newly recognized volcanic ash (VA), ICAO developed in 1982 a set of interim guidelines to assist States in the dissemination of information on volcanic ash to pilots, airlines, and ATS. It also developed preliminary contingency arrangements for the diversion of aircraft around areas affected by volcanic ash. Formal requirements were introduced in the relevant Annexes to the Chicago Convention and Procedures for Air Navigation Services (PANS), by the ICAO Council in March 1987. Appropriate guidance materials, together with the regular update of these requirements, have been introduced to improve the availability of information related to VA for international air navigation. Important milestones of the IAVW included the designation of nine volcanic ash advisory centres (VAAC) to detect, track, and forecast the movement of VA clouds in their areas of responsibility, and the establishment of the IAVW Operations Group (IAVWOPSG) and the International Volcanic Ash Task Force (IVATF). Currently, the Meteorology Panel Working Group on Meteorological Operations (METP WG/MOG) is responsible for the coordination and further development of the IAVW. Taking into account the recent and planned future scientific and technological advancements, there is a consensus within the aviation operational and scientific sectors involved in the IAVW that continuing work towards quantitative volcanic ash forecasts will greatly support the risk-based, dosage approach.

The Meteorology Divisional Meetings are typically held once every decade approximately, serving as ideal opportunity to bring together ICAO States and WMO Members to set out key recommendations on the enhancement of aeronautical meteorological service provision over the subsequent years. The following table provides the list of MET Divisional meetings held over the past years. It is to be noted that the Meteorology Divisional Meetings are usually held simultaneously with the Sessions of the Commission for Aeronautical Meteorology of the International Meteorological Organization (IMO) and, after 1950, of the World Meteorological Organization (WMO).







11 October to 2 November 1945


Meteorology Divisional Meeting


29 October to 16 November 1946


Meteorology Divisional Meeting


17 to 18 September 1947


Meteorology Divisional Meeting


14 February to 25 March 1950


Meteorology Divisional Meeting


15 June to 14 July 1954


Meteorology Divisional Meeting


1 September to 29 September 1959


Meteorology Divisional Meeting


20 January to 15 February 1964


Meteorology/Operations Divisional Meeting


13 to 17 May 1974


Meteorology Divisional Meeting 


14 April to 7 May 1982


Communications/Meteorology Divisional   Meeting


5 September to 28 September 1990


Communications/Meteorology/Operations Divisional Meeting



9 to 26 September 2002



Meteorology Divisional Meeting


7 to 18 July 2014


Meteorology Divisional Meeting


The purpose of this Annex 3 is to make provision of meteorological information to operators, flight crew members, air traffic services units, search and rescue units, airport management and other concerned with aviation. Aeronautical Meteorological (MET) information is pivotal to the safe and efficient conduct of civil aviation. Improving the accuracy and quality of this information in an increasingly globalized and capacity-constrained aviation operating environment is a prime objective.


Working arrangements between ICAO and WMO were agreed and approved by both organizations during 1953 (approved by the Council of ICAO on 21 May 1953 and by the Executive Committee of WMO on 23 October 1953) for entry into force on 1 January 1954; an amendment to those arrangements was approved by the ICAO Council on 26 November 1962 and by the WMO Executive Committee on 16 October 1962) to become effective on 1 January 1963. The arrangements were designed to secure close cooperation and to establish machinery regarding the allocation to one organization or the other of primary responsibility for certain sectors within the field of common interest. In accordance with that document, ICAO is responsible for specifying the needs of the users/customers of aeronautical meteorological services, whereas WMO is responsible for providing the aviation community with operational meteorological information. WMO and ICAO maintain close and constant cooperation in keeping under review the requirements of meteorological services for aviation and in the adoption of procedures for the provision of these services, as well as keeping them up to date.


United Nations New York – 9 February 1955 – First Day Cover

Tenth anniversary of the International Civil Aviation Organization

Picture of a meteorological station in Switzerland taken in the early 1950s, with a Convair CV-240 in the background. Built in 1937, the Sphinx Observatory, 3,571 metres up in the Jungfraujoch, is maintained by the Swiss Aeronautical Meteorological Service and symbolizes the vigilance of the world’s aviation meteorology networks over international air transport. Observations were made at that time between 6 in the morning and 7 at night.



16-Pages pamphlet available at ICAO’s counter during the Brussels Universal and International Exhibition in 1958.

The texts in this brochure were printed in three languages: English, French and Dutch.

This pamphlet describes ICAO’s mission and activities and shows the Sphinx Observatory, in Switzerland.

The same picture was printed on the front-page of ICAO Bulletin in August 1954.




Original picture of the Sphinx Observatory in the Jungfraujoch, Switzerland.

Service cover sent from the Civil Aviation and Meteorology Authority of Yemen Arab Republic (now Yemen)

to Yves Lambert, Secretary General of ICAO from 1 August 1976 to 31 July 1988.


United Nations Geneva - 26 June 1990 –

First Day Cover - 45th Anniversary of the United Nations

The close relationship among the UN Organizations is depicted on this issue. Numerous Organizations are represented by an identifier, in particular: ICAO by an aircraft and WMO by the sky and clouds.