But it's not talking about the aircraft itself. The article is talking about the comparison of the visual image of the aircraft and the sound coming from the ai

But it's not talking about the aircraft itself. The article is talking about the comparison of the visual image of the aircraft and the sound coming from the aircraft: "You can hear the loud engines, and your ears tell you it should be in one place, but your eyes tell you it’s clearly well ahead of its noise." What time the aircraft passes the observer is irrelevant (if you Ctrl+F for pass in the original article, it's not there) and the correct calculations for an aircraft traveling 100m/s would be: If you're 100km away, the image of the plane will reach you after 1.20 milliseconds (100km / speed of light in air), and the sound will reach you in 333s. (in which the plane now has moved 33.3km and now you're getting an image of a plane 66.7km away.) If you're 200km away, the image of the plane will reach you after 2.40ms and sound will reach you after 667s. The main thing this effect relies on is the ability for an object to move a significant fraction of its size in the time it takes for the sound to reach you.