In the year 3627 BBY, during the third Galactic War, the Eleventh Fleet stopped at Onderon on its way to Corellia to aid in the defense of the Meridian Complex. However, while on Onderon, it was targeted by the Sith Empire, which aimed to destroy it so that it could not be able to continue on to Corellia.
However, the Empire's plans to destroy the fleet were stopped by the Alliance Commander, who interrupted Darth Savik's droids before they could turn Onderon's Anti-aircraft guns against the fleet and destroy it.
Following this, the fleet arrived to defend against the attack on the Meridian Complex, and helped to successfully fight off the Imperial Fleets.
The Eleventh Fleet appears during the Onslaught expansion for the game Star Wars: The Old Republic. If the player character is a Republic Loyalist or an Imperial Saboteur, they will save the fleet from being destroyed by the Empire. However, if the player character is an Imperial Loyalist or a Republic Saboteur, they will successfully destroy the fleet and prevent it from being present during the defense of the Meridian Complex.