What is this movie called?

The only thing I remember about it is that it seems like it's the "never ending story movie" but it's a cartoon. It has this loooonnnngggg white dog dragon thingy, and this boy goes around flying on him trying to sop the bad guys. Yet again, it reminds me of the movie "the Never Ending Story" but it's not it. Because the movie I'm thinking about is a cartoon not live-action.