Highlighting the clouds which roll and play over and around the top of planes' wings.

These are a byproduct of the lift forces which hold aircraft up in the sky. Lift comes about because the air pressure is low above the wing, and a drop in air pressure (and temperature) tends to cause invisible water vapor (gas) to condense into the visible water droplets (liquid) we see as clouds.

The misty show is most obvious during landing and takeoff as the plane is tilted upwards to increase lift at these times.