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In a typical crash, for example, the weather is poor—not terrible, necessarily, but bad enough that the pilot feels a little bit more stressed than usual. In an overwhelming number of crashes, the plane is behind schedule, so the pilots are hurrying. In 52 percent of crashes, the pilot at the time of the accident has been awake for twelve hours or more, meaning that he is tired and not thinking sharply. And 44 percent of the time, the two pilots have never flown together before, so they’re not comfortable with each other. Then the errors start—and it’s not just one error. The typical accident involves seven consecutive human errors. One of the pilots does something wrong that by itself is not a problem. Then one of them makes another error on top of that, which combined with the first error still does not amount to catastrophe. But then they make a third error on top of that, and then another and another and another and another, and it is the combination of all those errors that leads to disaster. These seven errors, furthermore, are rarely problems of knowledge or flying skill. It’s not that the pilot has to negotiate some critical technical maneuver and fails. The kinds of errors that cause plane crashes are invariably errors of teamwork and communication. One pilot knows something important and somehow doesn’t tell the other pilot. One pilot does something wrong, and the other pilot doesn’t catch the error. A tricky situation needs to be resolved through a complex series of steps—and somehow the pilots fail to coordinate and miss one of them. “The whole flight-deck design is intended to be operated by two people, and that operation works best when you have one person checking the other, or both people willing to participate,” says Earl Weener, who was for many years chief engineer for safety at Boeing. “Airplanes are very unforgiving if you don’t do things right. And for a long time it’s been clear that if you have two people operating the airplane cooperatively, you will have a safer operation than if you have a single pilot flying the plane and another person who is simply there to take over if the pilot is incapacitated.
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