When we observe airplanes flying from the ground, they appear to move very slowly, mainly due to visual illusions and the distance effect. This phenomenon has several key reasons:
Firstly, when airplanes fly at high altitudes, they are very far from the ground. Due to the distance effect, we perceive the speed of airplanes as slow because our eyes find it difficult to detect small movements of distant objects.
Secondly, there may be a lack of sufficient visual reference points in the sky, such as buildings or distinctive terrain features, which makes the speed of airplanes appear even slower.
Lastly, human vision has limitations in perceiving the speed of distant objects. Even when airplanes are flying at considerable speeds, our perspective from the ground tends to make their flight appear slow.
In reality, most commercial airplanes fly very fast, typically exceeding speeds of 500 miles per hour (800 kilometers per hour). However, due to the visual effects mentioned above, airplanes appear to move at a slow pace when observed from the ground.