Contrails are a product of combustion ejected from the aircraft engines.
And when a contrail forms near the sun, sometimes, there is a beautiful rainbow effect visible. Like in this picture:
These rather rare iridescent clouds are created through light diffraction in small water droplets or small ice crystals.
This photo was taken by Ron Smith at Henstridge, Somerset, UK. Learn what contrails are in this article.
As explained by AtOptics: “The aircraft was flying from East to West and, when first seen, was only producing an intermittent contrail. The iridescent contrail appeared as the aircraft approached a cloud layer just below its flight altitude.”
A man-made natural sky phenomenon… But what if it was something else?