Question

The sky appears dark to passengers flying at very high altitude

Hint:

The sky appears blue due to scattering of sunlight by air molecules. At high altitudes, there is less scattering, so the sky appears dark.

Answer 1

At high altitudes, the atmosphere is less dense, resulting in reduced scattering of sunlight due to fewer air molecules.
Light scattering causes the blue color of the sky at lower altitudes. However, at higher altitudes, this scattering diminishes significantly, making the sky appear dark.The sky appears dark to high-altitude passengers because of this decreased light scattering.