Phantom flyers

This falls more under cryptozoology, but it's fascinating. From The Guardian:

The notion that large, hitherto unidentified creatures may exist in our oceans and wildernesses is one that most people are comfortable with. But could colossal, primitive lifeforms, invisible to human eyes, also populate our skies?

Trevor James Constable, sailor, aircraft historian and scientific iconoclast, certainly thinks so. Inspired by Wilhelm Reich's orgone energy, Ruth Drown's radionics, the writing of Charles Fort and Arthur Conan Doyle's story The Horror of the Heights, Constable became convinced that the UFOs he heard so much about in the 1950s weren't alien spacecraft, but living beings. Armed with a camera fitted with high-speed infrared film and an ultraviolet filter, Constable set out to reveal these sky beings to the world. His photographs certainly show something. To the untrained eye they look like discolorations produced during the developing process. But stare long enough and they take on the appearance of floating, zeppelin-sized amoebas.

I heard this theory on Art Bell's Coast-to-Coast AM years age and find it fascinating.