A limbless creature obviously can't have conventional wings and could suffer many problems in the blastoff.
Of cousrse I know the existance of the flying snakes, which are actually gliders. But I was thinking problem with the flying snake for this model is that they use flexible ribs to expand the surface area and slow down, using flexible ribs, this looks mutually excluyent with have a powered flying with resistant and strong bones (like a bird keel) for muscle attachment to permit the flapping to impulse the flight.
And other problem that this creature could is comparing with all the real flying all animals is that all them have had short bodys, I remember this is because long and flexible bodys or just tails increase the drag resistance of this animals causing that the required energy to fly increase much more.
So how a limbless creature could evolve powered flight, remembering the blastoff and stay in air?
Other things that could import for are the used bones and muscle changes.