Sardo joined the Empire to help secure it during the Galactic Civil War. As a near human, he wasnt allowed to be given a commission and instead worked as a non-commissioned technician aboard a variety of ships, being passed around by commanding officers who didn't want an alien on board.
After the destruction of the Death Star above Endor, and the subsequent actions of operation Cinder, many pilots defected to the New Republic. This shortage of pilots and new recruits led to Sardo being made a fighter pilot in addition to continuing to work as a technician.