At least five species of snake from the genus Chrysolopea in Asia are able to fly. Sort of.
As video of the reptiles show, they undulate from side to side, in almost an air-slithering, to create an aerodynamic system. It allows them to travel from the top of the biggest trees in the region (almost 200 feet high) to a spot about 780 feet away from the tree's trunk.
Now the US Defense Department, through it's sometimes eccentric seeming DARPA research fund, is sponsoring research at Virginia Tech to determine how the snakes do that. The research could then be applied to building new aircraft.
It gets stranger. During a technique not yet understood, some of the snakes can actually turn in air. What's more, they all take a flying leap off their perch to get airborne, then drop for a while to pick up speed before starting the motion that keeps them aloft much longer than they would otherwise.