Final answer:
The length of a train of package carts or containers is based on site-specific procedures and equipment capabilities. There is no set length as it varies according to the type of containers and carts used.
Step-by-step explanation:
The length of a "Train" of package carts or air containers (igloos) is determined by site/equipment specific procedures. Therefore, there isn't a universal answer to how long a train can be. These procedures take into account the type of cart or Unit Load Device (ULD) used. For instance, if standard 10-foot containers are being used, the overall length of a connected train of carts will need to comply with the specific guidelines of the transport facility or equipment capabilities and safety regulations. In areas such as airports or shipping docks, these procedures are crucial to ensure efficient and safe transportation or handling of cargo.