Which of the following does NOT affect aircraft performance?

Time of day does not have a direct impact on aircraft performance in the same manner as temperature, aircraft weight, or humidity. While factors like temperature and humidity are critical in determining air density, which affects lift and engine performance, and aircraft weight directly influences takeoff distance and climb rate, the time of day itself does not inherently alter these factors.

In fact, the effects of temperature and humidity can vary throughout the day, causing variations in performance related to these two elements. For instance, warmer temperatures during the day can lead to reduced engine performance and longer takeoff distances due to decreased air density; higher humidity might also affect engine efficiency and lift. However, these changes are linked to specific weather conditions rather than the time of day itself, making the time of day an unrelated consideration in terms of performance metrics. Thus, it stands apart from the other options as not directly influencing aircraft performance.