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In 1977, at Tenerife in the Canary Islands, heavy accents and improper terminology among a Dutch KLM crew, an American Pan Am crew and a Spanish air traffic controller led to the worst aviation disaster in history, in which 583 passengers perished.

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In 1980, another Spanish air traffic controller at Tenerife gave a holding pattern clearance to a Dan Air flight by saying "turn to the left" when he should have said "turns to the left" - resulting in the aircraft making a single left turn rather than making circles using left turns. The jet hit a mountain killing 146 people.

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In 1990, Colombian Avianca pilots in a holding pattern over Kennedy Airport told controllers that their 707 was low on fuel. The crew should have stated they had a "fuel emergency," which would have given them immediate clearance to land. Instead, the crew declared a "minimum fuel" condition and the plane ran out of fuel, crashing and killing 72 people.

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In 1993, Chinese pilots flying a U.S.-made MD-80 were attempting to land in northwest China. The pilots were baffled by an audio alarm from the plane's ground proximity warning system. A cockpit recorder picked up the pilot's last words: "What does 'pull up' mean?"

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In 1995, an American Airlines jet crashed into a mountain in Colombia after the captain instructed the autopilot to steer towards the wrong beacon. A controller later stated that he suspected from the pilot's communications that the jet was in trouble, but that the controller's English was not sufficient for him to understand and articulate the problem.

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On November 13, 1996, a Saudi Arabian airliner and a Kazakhstan plane collided in mid-air near New Delhi, India. While an investigation is still pending, early indications are that the Kazak pilot may not have been sufficiently fluent in English and was consequently unable to understand an Indian controller giving instructions in English.

(Aviation Today: Special Reports, 2004)