Every minute the ship is sitting by the pier not being loaded or unloaded, money is lost. Ships traveling are to their destination are making shipping companies money. The time that it takes to unload a cargo ship varies significantly and can take up to 30 days. This is a result of a variety of factors. Timing of when ships arrive, limited pier access and the time it takes for crane operators to safely move all the cargos to the shore for inspections.
Currently gas powered drones have a capacity of carrying 5 ton load which cover most dry containers and have the ability to operate for 50 minutes. There could be multiple drones that are flying different routes concurrently to service ships that are not docked on the pier.
Docking could be expanded to other area of the pier from just where the cranes could reach.
Jeff Bezos of Amazon is focusing their efforts on commercial door to door delivery of products to end consumers from the distribution center. The focus of this problem is the leg of transport of containers to the distribution centers. The earlier leg of transport could be achieved by flying containers directly from the ship to the delivery 18 wheeler truck. Alternately, from the 18 wheeler truck unloaded and shipped via drone to the consumers home or business.
First mover advantage. Increasing efficiency from taking the containers off cargo ships quicker with drones allows for more ships to enter the limited number of piers. Ships spend more time traveling than being idle and waiting to be unloaded or loaded. Shipping companies would concievably pay more to have a quicker ability to load and unload their ships so they could make money transporting.