Main Line Operator (MLO)
A Main Line Operator (MLO) is a shipping line that runs the principal deep-sea (long-haul) services between major ports on the world's trunk routes, using large vessels. MLOs are the carriers whose ships cross oceans on the backbone trades — as distinct from feeder operators, which run smaller vessels connecting minor ports to the main-line hubs.
The distinction reflects the hub-and-spoke structure of container shipping: MLOs concentrate volumes on efficient big-ship services between hub ports, and feeders distribute containers to and from the surrounding smaller ports. Cargo from a minor port is often feedered to a hub and then loaded onto an MLO's mainline vessel (transhipment). Knowing whether a service is main-line or feeder helps shippers understand routing, transit time and transhipment in their shipments, and is basic vocabulary in liner shipping.
Container shipping runs on a hub-and-spoke model, and the MLO-versus-feeder split is its basic structure — big ships on the trunk routes, feeders filling in the rest. Understanding which is which explains a shipment's routing, transhipment and transit time, and is essential vocabulary for anyone reading liner schedules.
What is the difference between an MLO and a feeder operator?
An MLO runs the main deep-sea services between hub ports with large ships; a feeder operator runs smaller vessels connecting minor ports to those hubs.
How do MLOs and feeders work together?
Cargo is feedered from a minor port to a hub, then loaded onto an MLO's mainline vessel — the hub-and-spoke transhipment model.