nubbsgalore:

three separate off duty commercial aviators photographed cumulonimbus clouds illuminated by flashes of lightning from their planes.

otherwise known as thunderclouds, cumulonimbus are the only cloud type that can produce hail, thunder and lighting. the base of the cloud is often flat with a very dark wall like feature hanging underneath, and may only lie a few hundred feet above the earth’s surface.   

cumulonimbus clouds are created through convection, often growing from small cumulus clouds over a hot surface.they get increasingly big until they represent huge powerhouses, storing the same amount of energy as ten hiroshima sized atom bombs. 

although the storm looks formidable, today’s airliners have advanced equipment to circle around storms this big without entering any dangerous zones.

(photos x, x)