Wikipedia:POTD column/May 2, 2006

Coloured smoke reveals a vortex of air created by the wing of an airplane, also known as wake turbulence or jetwash. This turbulence can be especially hazardous during the landing and take off phases of flight, where an aircraft's proximity to the ground makes a timely recovery from turbulence-induced problems unlikely.

Photo credit: NASA Langley Research Center
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