Never mind the cult movie Snakes on a Plane - scientists have shown how some serpents can fly.

Snakes were observed "slithering" through the air in an Asian rainforest. Adopting an S-shape, they were able to glide almost 100 feet from tall trees.

"They look like they are swimming," said study leader Dr Jake Socha, from Virginia Tech Wake Forest University in the US. "They turn their whole body into one aerodynamic surface."

Dr Socha's team found that flying snakes flex their ribs to stretch and flatten out their bodies. Looked at in cross section, they turn from a circle to an arched semi-circle.

"It looks like someone's version of a UFO," Dr Socha added.

Using a 3D printer, the scientists produced a rod with the same profile as a gliding snake's body and placed it in a tank of flowing water.

Although water is much more dense than air, the experiment recreated the effect of air flowing over a snake's body.

At most angles, the unusual body shape generated sufficient lift to keep the creature aloft.

However, the results published in The Journal of Experimental Biology do not fully account for the performance of flying snakes.

"If you make a rough estimate of the lift to drag ratio for the real animal, it appears to do better than what we got from this study," said Dr Socha.

"So even though this shape produced more lift than we were expecting, it doesn't get us the glide performance that snakes can attain, giving us a hint that there is something in what the animal is doing aerodynamically that is not captured by the cross-sectional shape alone."