What is a common difficulty in seeing railroad tracks or other linear features during flight?

The vertical development of vegetation is a significant factor that can obscure the view of railroad tracks or other linear features during flight. Tall trees, dense undergrowth, and other types of vegetation can grow vertically to a point that they mask the linear features on the ground, making them difficult to distinguish from the air. This obscuration can lead to challenges for pilots who need to identify these features for navigation or terrain avoidance.

Other elements, such as weather conditions, can indeed affect visibility, but it is primarily vegetation that creates a substantial barrier to seeing these linear features from the altitude typically used during flight. The altitude of the aircraft can also influence visibility but often determines how well the pilot can discern features rather than directly obscuring them. The color of the tracks might not be as significant a factor since tracks can still be visible regardless of their coloration if they are not obscured by external obstacles. Prioritizing the impact of vegetation is essential for understanding the dynamics of visibility during terrain flight operations.