In the animated television series "Avatar: The Last Airbender," Aang does not die during the events of the series. Instead, Aang, the last surviving Airbender and the Avatar, successfully defeats the Fire Lord Ozai, ending the Hundred Year War and restoring balance to the world.
However, in "The Legend of Korra," the sequel series to "Avatar: The Last Airbender," it is revealed that Aang passed away at the age of 66. The cause of his death is not explicitly stated in the series, but it is mentioned that Aang faced significant health challenges later in life due to his time spent in the Avatar State and the injuries he sustained during the Hundred Year War.
Despite his passing, Aang's legacy lives on through his descendants and the new Avatar, Korra, who follows in his footsteps to maintain peace and balance in the world.