Cargo Harness

A cargo harness is a class of dragon harnesses created for the express purpose of hauling cargo for longer distances. Typically, the harness allows for a heavy or middleweight dragon to carry a cargo load under their belly while in flight. The harness is constructed of reinforced leather and rope in a netting configuration with a number of strapping points to secure cargo containers to the netting and avoid shifting within the harness area. 
Harnesses are typically created to the specific dragon to ensure comfort and a well fitting harness, in addition to accommodating for the dragon's crew complement. Some dragon companies maintain a small number of netting attachments that can be added to a dragon's standard flight harness for a shorter distance haul, though these versions are typically reserved only for emergencies or short trips due to the higher chance for injury to the dragon or the crew when using a poorly fitting harness attachment. 
Cargo being packed for shipping via cargo harnessed dragon is typically packed into padded bags with strapping rings sewn around the bag. Chests and crates are only used sparingly when shipping fragile or rigid items which would be damaged in bags. The chests are then wrapped in padding blankets and strapped to ensure corners and edges are padded to avoid injury in flight. 
Dragons hauling cargo rarely flight solo due to the extra weight of a filled cargo harness. Instead, they are typically joined by at least one other support dragon who can intercept or handle issues arising during the flight. Cargo dragons receive additional training to take off and land with the cargo harnesses at various capacities to ensure they aren't likely to hurt themselves in the process. 
Due to the expense and limits on the types of cargo able to withstand the conditions of dragon flight, most cargo is still sent overland unless there is an emergent need for the goods.