http://www.digitaljournal.com/article/300121

All international flights to use only English by March 2011

Posted Nov 12, 2010 by Sara Star
One language for both pilots and air traffic controllers - English has become the universal language, at least in international travel.
International airport Domodedovo  Moscow
International airport Domodedovo, Moscow
www.en.wikipedia.org
According the International Civil Aviation Organization (ICAO), air traffic control (ATC) allows for each country to use their own language, but upon request of the pilot, they must be able to communicate in English.
However, starting in March 2011, all international airports will be required to switch to one language, and one language only - English. By doing this, it enables all pilots to understand each other in the control zone and be aware what nearby aircraft are doing.
ICAO delayed this requirement for three years on request of several countries including Russia, giving pilots and air traffic controllers a grace period to become more proficient in English, at least a Level 4 knowledge, which is presently not mandatory.
Sergei Melnichenko, deputy head of the language school Kompleng, which has a program for aviation professionals, states, “The current level is adequate for standard flights, but in an emergency, more fluency is needed to give advice and make quick decisions, requiring at least Level 4 knowledge.”
This may occur more frequently than one would think. Luckily, a language barrier incident at the St. Petersburg's Pulkovo Airport resulted in a safe landing last March. According to Moscow Times, a Swiss Air flight taking off hit a flock of birds, which immediately resulted in vibrations in both engines. During the Mayday call, the air traffic controller was having trouble understanding the problem for several minutes until a pilot on another plane translated in Russian. The Mayday call can be heard on this youtube video.
ICAO is an agency of the UN with its headquarters in Montreal, Quebec, Canada.