An airport has occasionally been closed to large planes because of weather conditions that do not entail storms or low visibility. Instead, the conditions combine to create an unusually low air density. Explain why such an air density would make it difficult for a large, heavy plane to take off, especially if the runway were not exceptionally long.

An airport has occasionally been closed to large planes because of weather conditions that do not entail storms or low visibility. Instead, the conditions combine to create an unusually low air density. Explain why such an air density would make it difficult for a large, heavy plane to take off, especially if the runway were not exceptionally long.