The Vanship Union is an organization responsible for mail delivery in the country of Anatoray.
People who have letters or packages they wish to send submit requests to the local Vanship Union, including details of the job. Based on these details, the Vanship Union assigns the job a difficulty ranking from one to ten stars. A simple delivery is one star, while a delivery into a war zone is three stars; the mission that Claus Valca completed for the Silvana was 7 stars; the only mission that was ever ranked ten stars was the delivery of a peace treaty from Anatoray to Disith, something which required flying through the Grand Stream -- believed to be impossible. The Vanship Union then posts the requests along with their difficulty ratings; vanship pilots select missions based on their level of piloting skill. After selecting a mission, the vanship couriers are given the address to pick up the mail and the payment; the price is proportional to difficulty. Upon delivering their mail, the couriers collect a signature, which they bring back to the Vanship Union as proof of delivery.
Later in the series, many pilots in the Vanship Union join the Alliance.