In a story June 20, The Associated Press reported that airplanes take off and stay aloft because of lift, the force from the movement of air underneath the plane's wings that push it upward. The story quoted a scientist who explained that heat makes air expand and become less dense, reducing the amount of force the air can exert on the wings. The story should have made clear that lift is created by movement of air both above and underneath the plane's wing. The movement of air above the wing creates an area of low pressure. The movement of air below creates an area of high pressure. That difference pulls the plane up.
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