Air draft potentially limits port capacity, especially as increasingly larger vessels come into service. These restrictions may not affect all
terminals in a port. Some ports might have terminals with no air
draft restrictions (e.g., the container terminals at the Port of Virginia) because
no bridges cross their navigation channels. The following table shows the air drafts by limiting bridges for select ports and the online Port Profiles show what, if any, air draft or channel depth restrictions exist within the port vicinity.
Air draft restrictions may be eliminated as bridges are either raised or replaced. Several ports have constructed new bridges (e.g., in 2020, the new Gerald Desmond Bridge open at the port of Long Beach)  or elevated existing bridges (e.g., in 2019, the raising of the Bayonne Bridge completed at the port of New York/New Jersey).  The higher the bridge, the more stacked
containers that can pass under (e.g., 8-foot-tall containers can reach a
combined height of 144 feet when stacked 18 high aboard a megaship’s cargo
Air Drafts by Limiting Bridge for Select Container Ports: 2022
Channel depths can limit the size of vessels able to call at a port. The Pacific coast ports with their natural harbors, such as the ports of Long Beach and Los Angeles, have the deepest channels. The Mississippi River ports of Cincinnati-Northern Kentucky, Huntington, Pittsburgh, and St. Louis have the shallowest channels. Even if a port’s minimum channel depth allows for megaships, the individual marine terminals within the port vicinity may not have the minimum depth alongside to handle them. The following figure shows channel depths for select ports.
of Long Beach, The Gerald Desmond Bridge Replacement Project,
available at https://newgdbridge.com/ as of October 2021.
Port Authority of New York and New Jersey, Navigational Clearance
Project, available at https://old.panynj.gov/ as
of December 2021.