The All Terrain Anti-Aircraft walker, known more commonly as the AT-AA, is an advanced vehicle available to the various playable Imperial factions in Eras 1–5. It is equipped with a Flak Gun for its weapons system.
Manufactured by Rothana Heavy Engineering, the AT-AA was designed as an anti-aircraft platform with limited offensive capabilities against any other vehicle. Preliminary designs were seen as far back as the Clone Wars, but the unit did not enter service until the New Order's rise. The walker saw heavy action during the Galactic Civil War, and were found especially effective against the Rebellion's T-47 Airspeeder.
The AT-AA is the anti-aircraft support of the Imperial Factions. It does what is says on the package: destroys enemy aircraft better than any other unit. This is important, especially against the New Republic and the Empire of the Hand in later eras when they have V-wings and AirStraekers respectively. They also have the useful support ability of jamming missiles, making it nearly impossible for PLEX troopers and other missile launching units to do any damage.
The weakness of the AT-AA is its inefficiency against anything not aircraft. They must have an escort to avoid being destroyed. In short, the AT-AA is an effective anti-air vehicle with missile jamming capabilities.