While we're on the subject of international languages, the choice of languages at the United Nations is interesting. The original official languages were English, Chinese, French, and Russian, not coincidentally the languages of the permanent members of the Security Council. The choice was largely political. English had perhaps the strongest case. Not only was it already widely used as an international language, it was the dominant language of the United States, which had emerged as the greatest military and economic power. Chinese too was the language of a major power, as well as the most widely spoken language. Russian was the language of one of the major powers though not particularly widely spoken outside of the Soviet Union. French was chosen because it was still widely considered the international language of diplomacy. Spanish and Arabic were added in 1973, in both cases because they are the languages of a score of nations.
Although in theory all six languages have equal status, some languages are more equal than others. English, French and Spanish are the working languages of the General Assembly; English and French are the working languages of the Security Council. Public information is often not translated into Spanish, Arabic, and Chinese. This led to a protest in 2001 by the representatives of the Spanish-speaking countries.
Some people think that the UN spends too much money and effort on translation and interpretation and that it should adopt a single official language. Here is the proposal of the Transnational Radical Party and Esperanto International Federation that the United Nations adopt Esperanto as its official language. Others want to add official languages. There is pressure to add Hindi. This site advocates the adoption of Hindi as an official language of the UN. And here is a speech by the Indian Ambassador to the UN.
The irony in all this is that it appears to be purely symbolic. The sort of people likely to end up as diplomats or staff at the United Nations almost all speak English. When the UN surveyed its member nations as to which of the official languages they would prefer to receive correspondence in, 130 opted for English, 36 chose French and 19 Spanish. Not a single country preferred Arabic, Chinese, or Russian.