A ICAO está sediada em Montreal porque era o resultado de uma votação dos membros fundadores (PICAO é o ICAO Provisório):
Why was Montreal selected? While insisting on the excellent hospitality offered since of the beginnings of PICAO by the federal, provincial and municipal authorities, the delegates described Montreal like a roundabout of the international means of communication and a strategic centre with a formidable economic, scientific, technical and aeronautical expansion being felt for a few years. One insisted on the vast spaces of the Canadian territory, offering unlimited possibilities for the scientific and practical experiments in the field of aviation. Moreover, PICAO was to be established as close as possible to the central head office of the United Nations.
E a IATA está em Montreal porque seus estatutos fundadores disseram que deve estar no mesmo local que a ICAO :
Article II of the IATA 1945 Statutes states that “The Head Office of this Association shall be maintained in the city in which the headquarters of the International Civil Aviation Organization is located.”; this article was later amended to leave an opening for a possible other place as determined by the General Meeting