There have been, over the centuries, a number of reports of serpents in the sky.
1762 - A snake reported in the sky over Devon, England. It was described as 'twisting'. It seems to have been generating light.
1811- A fiery serpent in the shape of a horseshoe was seen over Geneva, Switzerland.
1857 - A serpent (or something that looked like one) seen over Missouri was said to be breathing fire and to have streaks of light along its sides.
1873 - At Bonham, Texas, something "resembling" a yellow striped serpent the length of a telegraph pole was descried in the air by a farmer and others. In the same year something similar was seen over Fort Scott, Kansas.
2000 - A wayfarer in Spain in the El Encinar de Boadilla area claimed to have seen what looked like a snake colored silvery white in the sky.
One has to ask if these were really animals or artificial craft of an unknown nature.
The link below leads to a long article on serpents in the sky.