About shadows:

The two planes are probably flying no more than 2000 ft AGL. Restored warbirds burn a lot of expensive avgas and who would want to waste fuel climbing to a high altitude. They are near their base at Hickory and just out enjoying a beautiful winter afternoon.

At 2,000 AGL a ground shadow should be apparent.

I don't know a thing about aerial photography and thank Cyclonic for providing some insight.

Hill raises some good points. The break observed shows the terrain to the north being shot at a much earlier hour.

That planes at high altitude do not generate a discernible ground shadow is true, although from 39,000 ft looking directly downsun you will see a halo type circle apparently on the ground or intervening atmoshere. There is a name for this phenom but being old I forget what you call it