While there is a genus of snake known as the Flying Snake (Chrysopelea), cryptozoologists speaking of such things are rarely referring to this beast, which in fact proceeds by gliding. Cryptozoologists are in fact far more interested, as a rule, in those volant serpents whose flight cannot be so easily explained.
One has the impression, however, that some of these just might be mechanical devices, operating at a time when such devices should not have been possible.
Take, for example, one reported from Devon in 1762. This is described as "twisting", but it also seems to have generated light. Is it possible that some lone inventor, working in his laboratory in the south-west of England, managed to invent a flying device with an electrical component? In 1873 at Bonham (Texas) an object that looked like a snake but was the length of a telegraph pole and had yellow stripes was seen by a number of persons, while later in the year something similar was seen over Fort Scott (Kansas). In 1857 another such "snake" was reported from Missouri. The description of this one was particularly interesting from the machine angle, for it was said to be breathing fire and to have streaks of light along its side. This sounds as though it could in reality be a powered vehicle. Those who hadn't considered the possibility of such a vehicle could well have identified it as a serpent.
Could these supposed cryptids, then, have been not cryptids but machines? We haven't sufficient evidence concerning them, but it is a possibility worth bearing in mind.