Originally, Fedex (at least the overnight portion) was designed as a single-hub system. Packages were gathered up regionally and put on a plane. All of these planes then flew to Memphis, TN. All the planes get unloaded, sorted, and reloaded with packages to be delivered to their region.

When the founder submitted this business proposal in college, he received a C with his professor telling him it was unrealistic (oops!).

I wouldn't be surprised if this system has been expanded to include other regional hubs, especially out of busy regions like LA.