Winged Nazgûl
From Tolkien Gateway
After their discomfiture at the Ford of Bruinen by Elrond and Gandalf, the Nazgûl returned to Sauron their master in the land of Mordor. There, he furnished them with horrible winged mounts and sent them abroad once again. While mounted on these flying beasts, they were known as the Winged Nazgûl.
