Why often have white smoke streaks in the sky after the plane flies over?

Sometimes, the planes will leave white long streaks in the clear blue sky, they will fade and disappear later. So, what are those white streaks?

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The white stain is the exhaust of an airplane engine that is emitted in the sky and due to the difference in temperature and humidity in the air that causes the steam in the exhaust gas to condense in the atmosphere. This is the same as when we breathe on cold days.

The streaks of white smoke created by planes are not the same, sometimes it is a very long trail in the sky but sometimes they vanish very quickly after forming. And based on that difference, we can predict the weather.

1. Thin, tan white streaks show that the air has low humidity, signaling a beautiful sunny day.
2. Thick, long-lasting white streaks show that the atmosphere is extremely wet, predicting a thunderstorm or storm.