Article: Russian is one of the official languages (or has similar status and interpretation must be provided into Russian) of the United Nations, International Atomic Energy Agency, World Health Organization, International Civil Aviation Organization, UNESCO, World Intellectual Property Organization, International Telecommunication Union, World Meteorological Organization, Food and Agriculture Organization, International Fund for Agricultural Development, International Criminal Court, International Monetary Fund, International Olympic Committee, Universal Postal Union, World Bank, Commonwealth of Independent States, Organization for Security and Co-operation in Europe, Shanghai Cooperation Organisation, Eurasian Economic Community, Collective Security Treaty Organization, Antarctic Treaty Secretariat, International Organization for Standardization, GUAM Organization for Democracy and Economic Development, International Mathematical Olympiad. The Russian language is also one of two official languages aboard the International Space Station - NASA astronauts who serve alongside Russian cosmonauts usually take Russian language courses. This practice goes back to the Apollo-Soyuz mission, which first flew in 1975.

Now answer this question: When did Apollo-Soyuz fly?
1975