CT-4981, given the nickname Contrail, was a Clone trooper pilot who fought as a part of Shadow Squadron. Shadow Squadron was led by Jedi General Anakin Skywalker. Contrail was given the call-sign Shadow Eleven. Contrail also piloted a Y-wing starfighter.
Like all Clone troopers in Star Wars: The Clone Wars, Contrail was voiced by Dee Bradley Baker. He has only appeared in Season 1, Episode 3, but it was to identify one of the Shadow Squadron pilots that are not normally shown. Shadow Squadron helps the Republic throughout the Clone Wars. His presence can be implied, as well as other identified Shadow Squadron pilots such as Broadside and Matchstick.
Just like all the other clones, he was the clone of infamous bounty hunter Jango Fett, and was created on the planet Kamino and trained there as well. During the Clone Wars, he was assigned to Shadow Squadron, a unit of elite starfighter pilots. They're motto: "Minimum casualties, maximum effectiveness. That's us". Anakin Skywalker chose Shadow Squadron for their renowned efficiency in order to destroy General Grievous's ship, The Malevolence. The Malevolence was an incredibly dangerous heavy cruiser spacecraft with a powerful dual ion cannon superweapon that could disable entire fleets with an EMP. It's power worried the Republic, and Shadow Squadron's clean record was tested in Grievous's campaign. However, Contrail and his fellow pilots would succeed.
Following this arc, Contrail would never be seen again in the TV series. However, this was not the last of Shadow Squadron, as their assistance was later shown during the Battle of Kamino. While not shown, Contrail continued to help the Republic with his experience throughout the Clone Wars. Contrail and Shadow Squadron would go on to experience many skirmishes in the galaxy during the Clone Wars, surviving until its very end.
Many years later, it is revealed that he continued to served the Empire and witnessed the destruction of the superweapon Tarkin. Taking a shuttle in search of survivors, Contrail located and rescued Darth Vader from his starfighter and brought him to Hockaleg, only to find that the local population had rebelled against the Imperial rule in the aftermath of the superweapon's destruction. He then sacrificed himself to save Vader by shielding him from enemy blaster fire with his body. Before Contrail died, Vader comforted the clone, commending his piloting skills.