What exactly is the white we see coming off an airplane in the sky.
Sometimes in the summer you can lookup and see many streaks in the sky.
They are much longer and last longer in the summer than winter. Please
tell me what causes this and why they last longer in the summer.
The white streaks you see coming off airplanes are called contrails. That
is short for condensation trail. Contrails are actually clouds made by the airplanes.
An airplane's exhaust has some water vapor in it, just like the air.
Sometimes when the exhaust mixes with the air, it has so much water vapor
that the air can't hold it all. The water vapor then turns into clouds.
That's why you sometimes see contrails following jet airplanes.
The air has more water vapor in it during the summer. That means that
it's more humid than during the winter. Contrails will last longer
during the summer because the clouds won't evaporate very fast in the
Submitted by Stephanie (age 27, Ohio, USA)
January 16, 1998
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