Many times when a plane is flying high in the sky, it leaves long white streaks that last for hours.

And Frankie, scientists say these are in fact clouds, they're called 'contrails'.

The word is short for condensation trail.

Scientists say this is normally caused by the hot exhaust coming from a jet plane.

Scientists say the air high in the sky is low in temperature and has low vapor pressure.

So when the hot humid air from the jet exhaust mixes with it, a cloud is formed, creating the long streaks that you see from the ground.

Another kind of contrail is formed by the jet's wing.

Scientists say air moves over the wing really fast and cools in the low temperature.

The cool air can't hold much water, so a lot of it condenses and forms a contrail.

Thanks for your question Frankie!

If any of you have an interesting question you'd like answered...ask me!

Send it to my inbox at John.Rogers@wctv.tv

Let me know your name and where you're from and if you're lucky....I'll answer it LIVE next Sunday!