My dad used to fly charters between Africa and the Middle East. Imagine the myriad of African, Middle-eastern, European and American accents all trying to communicate life-and-death information using a "common" language!
Apparently, to be an air traffic controller there is no requirement that you can be
understood in English, only that you can speak it. Picture an Iraqi pilot talking to an Israeli controller in a language neither of them uses at home, each mangling the language in their own regionally-distinct way.
When aircraft travel across the Atlantic ocean, they are largely on their own when out over uncontrolled airspace. As they approach Europe, they check in with controllers in Shannon, Ireland and then receive vectors to their final destinations. Once, a mis-communication (likely a pilot from the American south talking to an Irish controller) resulted in an incorrect vector. They pilot dutifully entered the coordinates and the plane flew itself to the wrong airport. Because the crew realized the error too late, they had to land in Frankfurt and then take off again for Copenhagen, their intended destination.
What makes that story hilarious to me is that this 747 was one of the first equipped with seatback entertainment consoles. If you've ever flown across the Atlantic or the Pacific, you've probably been fascinated by the global map showing your plane's position (plus altitude and outside temperature) as you track your progress around the world. Well, the crew may not have realized they were on the wrong vector,
but every passenger knew! Imagine their concern, knowing the plane was off course with no explanation from the cockpit.