A group of specialised GTS freighters and their fighter escort
The Galactic Trading System or 'GTS' is an organisation set up by the League during its Golden Age, to facilitate trade between the League's members. Every member planet of the League is automatically signed up to the GTS and they set up trade routes to other worlds in order to supply planet with resources they need. For example, during wartime, the GTS will grant extra resources to planets in need of aid, and likewise refuse trade to planets that are attacking others. This is one of the League's many methods of sanctioning aggressors during wartime.
However, they have other civilian duties too. The GTS is responsible for the ferrying of certain supplies, and the protection of freighters on the move. Not all freighters involved in trade belong to the GTS, but they are all under GTS protection.
The GTS supplies worlds as far out from the Milky Way Galaxy as necessary, even crossing into other Galaxies that the League controls. Each Galaxy has its own version of the GTS but they all co-operate to expand trade routes to all inhabited worlds. The GTS even sets up trade routes to dangerous planets, like Skirrid and Mustafar, in order to boost trade options for members of the League.
Overall, the GTS is one of the most successful organisations in the League, because it brings in a lot of money and benefits everyone. However, the one criticism that many people have for the GTS is its policy of not arming civilian freighters, and occasionally freighters will fall victim to attacks from pirates, most commonly Terminators. Because of this, most freighters are accompanied with at least one escort craft, usually armed with basic phasers, lasers, MAC cannons or plasma projectors.