Why Can't We See Planes When They Fly Over Us?

Have you ever stood outside on a clear day, earphones on, listening to the sound of a plane passing overhead and wondered where the plane actually is? The sound is distorted, and you find yourself looking in the wrong direction. Plane visibility often depends on several factors, including the altitude, atmospheric conditions, and sheer distance.

Factors Contributing to Poor Visibility

When you hear a plane, it can be challenging to determine its exact location. The sound is usually distorted due to the atmosphere’s conditions and the distance the sound has to travel. Additionally, the plane's speed and altitude make it difficult to pinpoint its exact position.

Example: Recently, I saw two fighter jets pass by. Despite their high speed, they were very easy to see. This goes to show that even fast-moving aircraft can be quite visible if they are at a relatively low altitude and in clear skies. However, for commercial airliners, it is much the same.

Airliners do not break the sound barrier, making it easier for us to track them visually. However, there are still challenges in seeing them, such as the presence of clouds or the horizon.

Atmospheric Factors and Obscuration

Approximately 40,000 feet above you is a plane cruising at a high altitude. That distance is a significant challenge to overcome when trying to locate the plane. The atmosphere acts as a barrier, with the haze above you making it difficult to spot the plane. On a 'clear day,' looking up at the vast expanse of blue sky, you would be hard-pressed to distinguish the white dot of a plane, unless you look well ahead of the sound it makes.

The sound of the plane travels much slower than light, meaning it takes around 35 seconds for the noise to reach you. By the time you hear the plane, it has already moved seven miles further along, making it a white dot at the horizon.

Climbing and Descending Flights

If you live on a flight path where aircraft are still climbing or descending, you might see planes more often. However, when they cruise at over 40,000 feet, it becomes much harder to spot them. At this altitude, the plane is a mere speck in the vast expanse of the blue sky, making it nearly invisible to the naked eye.

Conclusion: Plane visibility is a complex issue that depends on altitude, atmospheric conditions, and the distance sound travels. Understanding these factors can help explain why we often miss seeing planes flying over us, even if we can hear them.