This observation is impossible on a Flat Earth with a Sun 3000 Miles above.
We can clearly see the Sun on the Horizon from 43,000 ft. The clouds beneath us are illuminated from below but are dark on top.
This geometry is impossible on a Flat Earth.
Of course – it works just fine on a Globe.
This video also proves the Sun is below eye level. If it were at eye level or above the top of the clouds would be illuminated.