What atmospheric condition can lead to a decrease in lifting capability of an aircraft?

The presence of structural ice on the wings significantly decreases the lifting capability of an aircraft. Ice accumulation alters the shape of the wing, disrupting the smooth airflow over its surface. This disruption leads to an increase in drag and a decrease in lift, which is critical during takeoff, climb, or any other flight phase. When ice forms on wings, it changes the airfoil's profile, making it less effective in generating lift as per Bernoulli's principle, which states that lift is created by the difference in air pressure above and below the wing surface.

While high temperatures, high altitudes, and clear skies can affect aircraft performance, they do not directly impact the physical structure of the wings in the same manner that ice does. High temperatures reduce air density, impacting lift, and high altitudes similarly decrease air density, whereas clear skies do not present any immediate detrimental effects on lift. Each of these conditions may require adjusted performance planning but does not create the same immediate and severe reduction in lift as ice does. Thus, the presence of structural ice on the wings remains the most critical factor leading to a significant decrease in lifting capability.