Flying Bison
Air Temples are inhabited by exotic fauna, one species of which is the six-legged, three-toed, five-stomached, beaver-tailed, Flying Bison, giant domesticated flying beasts ridden by Airbenders. According to a behind-the-scenes interview with the show's creators, they are a hybrid between a bison and a manatee. These creatures have brown eyes, shaggy, light grey fur and a brown stripe that runs along their back, from tail-tip to forehead, where it terminates in an arrowhead. In "The Great Divide", Aang reveals that Appa has five stomachs. These creatures are the main source of transportation for Air Nomads.
Bison Whistle
All Flying Bison can use airbending to fly, utilizing their broad tails to steer through air currents and also to defend themselves. As shown in "Appa's Lost Days", they are also able to use their mouths and possibly their noses to Airbend. A fully-grown Flying Bison can easily weigh ten tons. They are revered by the Air Nomads, whose tattoos deliberately emulate their arrow-shaped markings, for inspiring the Airbending art, similarly to how Badgermoles inspired Earthbending. It was customary for young air nomads to choose an air bison to be their lifelong companion. Aang chose Appa at the Eastern Air Temple, when he was a baby calf, by giving him an apple.
To direct a Flying Bison to take flight, Aang uses the command "Yip-yip." To summon one from a far location, one may use a Flying Bison whistle. Though fairly docile, these creatures can be fearsome when aroused to fight. The most notable and possibly last surviving Flying Bison is Appa, Aang's pet and major means of long-distance transportation.