Rex's BTL-B Y-wing fighter-bomber

As a BTL-B Y-wing starfighter/bomber, the starfighter was equipped with two for propulsion. Its armament consisted of two front-mounted laser cannons and a rotatable SW-4 ion cannon controlled from the gunner's turret. The ship had extendable legs for landing on the ground. 23.4 meters in length, the bomber could carry three crew members: a pilot in its cockpit, a gunner in the central bubble turret, and an astromech droid in the onboard socket, situated to the rear of the gunner's turret. Accessible by a three-paned hatch, the cockpit contained controls to activate the starfighter's engines and to open the gunner's turret. The Y-wing had a largely white paint job, with blue stripes on its central body and grey markings down the length of the engines, which were also marked with the Republic crest in black.

The Y-wing was utilized by the Galactic Republic Navy late in the Clone Wars between the Galactic Republic and Confederacy of Independent Systems. In 19 BBY, the Y-wing was part of the onboard complement of the Venator-class Star Destroyer Tribunal when it was present above the planet Mandalore shortly after the end of the recent siege, in which the Mandalore resistance and forces of the Grand Army of the Republic had defeated the Shadow Collective and captured its leader, the rogue Sith Lord Maul. The Tribunal, under the command of former Jedi Padawan Ahsoka Tano and Clone Commander Rex, was to deliver Maul to the Jedi High Council on Coruscant. At the time, the Y-wing was docked in the Tribunals repair bay above an exit in the capital ship's bottom hull, and was the only ship in the repair bay not currently undergoing maintenance.

However, shortly after the Tribunal jumped into hyperspace, Dark Lord of the Sith Darth Sidious issued Order 66, a command which compelled the clone troopers of the Grand Army to turn on and execute their Jedi Generals through inhibitor chips implanted in their brains. Tano was forced to go on the run onboard the ship, releasing Maul from the detention level as a distraction before freeing Rex from the brainwashing with the help of three astromech droids, including her old unit R7-A7. Once Rex's chip had been removed, he and Tano attempted to escape the Star Destroyer. However, the escape pods had been destroyed because of orders Rex had given while he was brainwashed, so they were forced to head for the hangar, hoping to steal a shuttle.

Maul, left to his own devices, destroyed the Tribunals hyperdrive, setting the cruiser out of hyperspace and onto a collision course with a moon. When Tano and Rex reached the hangar control room, they discovered both that the starship was doomed and that the clone troopers, led by Clone Lieutenant ARC trooper CT-5597 "Jesse", had assembled in the hangar to try and prevent any escapes. Noticing that Jesse and his men were standing atop the lifts to the repair bay, Tano concocted a plan to make it easier for her and Rex to reach the shuttle by sending most of the clones to the maintenance level. However, while Tano and Rex were fighting off the remaining clones in the hangar, Maul entered and stole the Nu-class attack/transport shuttle in bay 12 that they had intended to take. Tano was unable to prevent Maul from escaping, being forced to let him go as Rex was in danger of being overwhelmed by clone reinforcements that had arrived. She cut a hole in the floor to bring herself and Rex down to the repair bay, with droids RG-G1 and CH-33P launching the lifts back up before the clones destroyed them.

Tano and Rex attempted to find another ship to escape in, but discovered that almost all of the ships in the repair bay were under maintenance and thus unflyable. After taking out some clones that remained in the bay, Tano spotted the Y-wing in its docking port and pointed it out to Rex. They repelled some more clones before running towards the starfighter, but the lifts began to descend as Jesse's forces had gained control of them. As Tano began to defend herself against their blaster fire, Rex continued running towards the Y-wing, shouting for Tano to get him over to the ship. When he reached the edge of the hole, Tano Force pushed him across the gap and onto the fighter, where he managed to get a grip on it as Tano turned her attention back to the clones' fire. Climbing onto the bomber, Rex stunned a few of the attacking clones before opening the cockpit hatch and getting inside.

At that point, the Tribunal had entered the moon's atmosphere, and the command bridge exploded, killing the bridge officers and setting the capital ship completely out of control. The clones and Tano lost their footing, and Rex, seeing the situation, took the pilot's seat and shouted for Tano to get over to the Y-wing. Tano leapt for the starfighter, but it was knocked free of its mooring and blown into the trail of debris flowing behind the doomed Star Destroyer, leaving Tano in freefall. Rex managed to activate the Y-wing after a brief struggle, getting it under control and flying it back towards the Tribunal. He looked around for Tano, opening the gunner's hatch when he finally found her. Tano grabbed the hatch, but lost her grip and was set flying again. As Rex followed her in the fighter, she slowed herself down by running along one of the Tribunals dislodged ion engines, and was able to successfully board the Y-wing after leaping off of it. Rex maneuvered the starfighter away from the ongoing crash, and he and Tano watched the Tribunal sink beneath the clouds.

Tano and Rex landed the Y-wing at the crash site, where they salvaged the remains of R7-A7 and other useful items, as well as burying the dead, as no one onboard the Tribunal had survived. As Tano spent a final moment at the graveyard, Rex walked back to the fighter and stowed a shovel he had used in a rack on its side, before turning back to look at Tano.

After leaving the moon, Tano discovered that her friend, Senator Padmé Amidala, had died. Tano and Rex travelled to Amidala's homeworld of Naboo so Tano could attend her funeral. Landing the starfighter in a river valley near the city of Theed, Rex stayed with the ship while Tano was gone. At the funeral, Tano was spotted by Alderaanian Senator Bail Organa, who was surprised that she had come despite the danger. When Organa asked her where her ship was, she told him it was by the river. Organa gave Tano a comlink to contact him with before the two parted ways, Tano evading shock trooper patrols before descending back into the valley and returning to the ship, whereupon she and Rex left Naboo.

Tano and Rex parted ways to go into hiding from the new Galactic Empire, the repaired R7 winding up with Trace and Rafa Martez, two sisters Tano had met after leaving the Jedi Order. Rex kept the Y-wing, and began working against the Empire. With the sisters' help, Rex tracked down Clone Force 99, a unit of rogue clones who had been immune to their inhibitor chips, and had them meet him on the junk planet Bracca to surgically remove them in a wrecked Venator. He landed the Y-wing in a wrecked hangar near the target ship's location in Bracca's starship graveyard, with the "Bad Batch" landing their shuttle Marauder next to the starfighter when they arrived. After the surgeries were performed, Rex parted ways with the squad as he had to make a rendezvous with a contact.

After the formation of the Galactic Empire, the Y-wing was owned and used by Captain Rex.

The Y-wing first appeared in the Star Wars: The Clone Wars series finale "Victory and Death."