In 2001, the International Civil Aviation Organization (ICAO) determined that English would, from then on, be the standardized language of air travel, and issued a directive that stated that all aviation personnel—pilots, flight crews, and air traffic controllers—must pass an English proficiency test. The mandatory compliance date was March 5, 2008. Not only must applicants know the appropriate aviation terminology in English, they must also be able to understand English instructions via radio, with no facial cues to prompt them. They also must learn to develop as benign an accent as possible, so that they are “intelligible to the aeronautical community.”
English has been the unofficial language of pilots for many years, but a tragic accident in the Canary Islands in 1977 emphasized the need for a universal aviation language. In this case, two 747 jets—one Pan Am, one KLM—collided on the runway at Tenerife airport. At one point, the KLM pilot told the tower in a heavy Dutch accent either “We're now at take-off” or “We’re uh…taking off.” The tower didn’t understand the message and told KLM to standby, but a simultaneous communication from Pan Am garbled the instruction. Reviews by the NTSB of the cockpit recorder transcriptions determined that the KLM pilot’s use of non-standard phraseology during the critical moments leading up to the accident contributed to the disaster.
Most of the 185 member countries of the ICAO had no problem with the English language proviso, save for three major airports: Charles de Gaulle in France, and Ottawa International and Montreal-Dorval International, both in Canada. It was partly because these three hubs wanted to communicate exclusively in French that the ICAO decided to actually put a law in writing.