Why do pilots see three suns while flying over the Himalayas?

High up in the sky, above the lofty Himalayas, pilots en route from Delhi to Kathmandu, or other high-altitude paths, often report seeing three suns in the sky at the same time.

This is not an optical illusion caused by cockpit reflections but an atmospheric phenomenon known as a sundog or parhelion.

SCIENCE BEHIND SUNDOGS

A parhelion occurs when sunlight is refracted through horizontally aligned, hexagonal plate-like ice crystals in cirrostratus clouds, which are thin, high-altitude, sheet-like clouds made of ice crystals that can cover the entire sky.

At altitudes above 6,000 metres, cirrostratus clouds appear as a thin, transparent veil, frequently creating a halo around the Sun or Moon. When ice crystals create bright spots around the Moon , the phenomenon is called a Moon dog.