Prior to the Hundred Year War, many flying bison lived on the Air temples. They were highly respected by the Air Nomads, regarding them as the first airbenders. While airbenders were in training, they each received a flying bison to become their lifelong companion. The sky bison was believed to be the only way in which people could reach an air temple.
After the Air Nomad Genocide, Appa was believed to be the last of the flying bison. However, during his adventures after the Hundred Year War, Aang discovered a new herd. Currently, a colony of healthy bison reside on Air Temple Island.
Flying bison have five stomachs, flat manatee-like tails, brown eyes, shaggy white fur, and a brown stripe that runs along their back from tail-tip to forehead, where it terminates in an arrowhead. They have six legs with three toes on each foot. A fully-grown flying bison can easily weigh ten tons. They are revered by the Air Nomads for inspiring the art of airbending, such as the badgermoles inspired earthbending, the moon began waterbending, and the dragons introduced firebending. The tattoos of an airbending master deliberately imitate the arrow-shaped markings of the bison.
The species Aang rediscovered after the Hundred Year War has a slightly different fur pattern with multiple brown stripes running down their backs, as well as brown ears instead of white.
All flying bison employ airbending to fly, using their broad tails to steer through air currents and to defend themselves. They are also able to use their mouths and possibly their noses to airbend. Though fairly docile, these creatures can be fearsome when aroused to fight, as is exhibited by Appa in many cases. These creatures were the main means of transportation for Air Nomads. It was customary for young Air Nomads to choose a flying bison to be their lifelong companion. Aang chose Appa at the Eastern Air Temple when he was a young child by giving him an apple. At the Northern Air Temple, airbenders held championships for bison polo. This game was played in the air; as airbenders rode their bison, they tried to force the ball with their polo mallet into an opponent's goal. To command their bison to take flight, both Aang and Tenzin use the command "yip-yip". To summon a bison from a distant location, it is possible to use a bison whistle. A sky bison whistle is used the same way as a dog whistle, which blows at a frequency that can be heard by humans but seems very quiet. It alerts the bison and sends it to its caller.
The flying bison is a hybrid between a bison and a manatee. The real-life bison shares a similar history to the flying bison, in that they were a very abundant species until foreigners came and hunted them down, reducing their numbers to near-extinction. Both have also been commonly misidentified as a buffalo.
During San Diego Comic-Con, it was revealed that Avatar Aang had discovered a whole new herd of sky bison. The new subspecies has a few differences; for example: old bison had four transversal stripes plus the last one that lies at the end of the tail, whereas the new species has more stripes that are thinner. The new bison also have brown fur on their ears instead of white.
The movement animation of the flying bison was heavily influenced by the similarly-shaped multi-legged Catbus in Hayao Miyazaki's movie My Neighbor Totoro. The series' creators have professed their love of Hayao Miyazaki's work in many interviews.
According to Avatar Extras, sky bison are the world's loudest snorers, with airbenders being second.
In Avatar Korra's time, the new species of sky bison that reside on Air Temple Island live in a series of caves. However, Aang's sky bison, Appa, had a fear of going in caves or underground for that matter, meaning that Appa's phobia was a personal trait rather than a behavioral trait in the species.