The BTL-S3 Y-wing starfighter was a variant configuration of the BTL Y-wing starfighter. It was used primarily by the Alliance to Restore the Republic.
The BTL-S3 was the most common Y-wing configuration. A two-man strike starfighter, the first crew member piloted the craft, while the second acted as a gunner and controlled the two swivel-mounted ion cannons, located right on top of the cockpit.
Many Y-wings of this variant were modified with defensive rapid-fire blaster turrets replacing the ion cannon turret, and particle cannons instead of the dual laser cannons on the nose. These Y-wings were used as heavy capital ship destroyers, and were eventually phased out by the new B-wing starfighters.
An S3 cockpit module detaches from the main body.
Luke Skywalker used this variant on his mission to Panna in 0 ABY, as did Princess Leia Organa and C-3PO on their journey to the Circarpous system.
The Deretta Destroyers, a mixed starfighter squadron of the Alliance to Restore the Republic, consisted of several BTL-S3s. Rebel pilot Tenk Lenso proved his skill as a gunner in the rear of a BTL-S3 while serving with the Destroyers.
The Rebel Alliance also used two-person Y-wings at numerous battles during the Galactic Civil War and at the Battle of Bespin.
Several of the BTL-S3s were stationed at Echo Base on the planet Hoth in 3 ABY. They assisted the base's T-65 X-wing starfighters in the evacuation of numerous GR-75 medium transports through the Imperial blockade of the planet. Rogue Squadron members Derek Klivian and Wes Janson escorted the transport Thon's Orchard to safety using a BTL-S3.
The Rebel Alliance-affiliated Bothan Blue Squadron used 12 Y-wings. Half of them were destroyed on the Raid on the Suprosa.
During the period after the Battle of Endor, Aggressor Wing's New Republic BTL-S3 Y-wing starfighters commanded by Colonel Horton Salm participated in the Battle of Brentaal IV, and later rescued Rogue Squadron during the evacuation of Ciutric.
A BTL-S3 as seen in the Star Wars Holiday Special
The BTL-S3 Y-wing starfighter first appeared in 1978's novel Splinter of the Mind's Eye, by Alan Dean Foster, and the first Expanded Universe novel.
Both Star Wars: Rogue Squadron: The Official Nintendo Player's Guide and Star Wars: Rogue Squadron II: Rogue Leader: The Official Nintendo Player's Guide mislabel the single-seat BTL-A4 Y-wing starfighter as the S3 variant.