It takes more time for sound to travel to location, thus one "hear" aircraft at one of the previous positions. Since light travels at much much speed, the plane is seen at its current position.
Explanation:
The speed of the sound in air = 344 m/s
The speed of the light in air = 3×10⁸ m/s
Since the speed of the light is way more than the speed of the sound in air and this when a high flying aircraft is being watched overhead , the person first sees the aircraft because the speed of light is much faster and <u>the sound of the aircraft come from behind the craft rather than from it is being seen because the speed of sound is very less as compared to that of light.</u>
