The Orlando International Airport appears to have been designed with significant functional modularity in mind.
MCO1) is clearly divided along functional lines. In reference to the diagram, the central portion is the “land side” and the four peripheral elements are the “air side” (per figure 1). You can easily find images of the actual airport via Google and see just how far apart the air side and land side are from one another. They are, in fact, essentially isolated from one another except for the connecting automated train systems used to move between them.
The two sides of the airport serve very different functions. The land side receives not only passengers, but also visitors, friends and family, and lots and lots of vehicles. Only the passengers need to get to the gates. While the land side must accommodate a very wide group of users, the air side is more specific - basically: planes and passengers. This difference allows each side to be more specifically “tuned” to respond well to the needs of their user groups. Generally, this kind of separation will lower overall complexity of the airport, making it (ceteris paribus) easier to run and maintain, more cost-effective, and more pleasant for its users.
And let's not forget security. While MCO's general layout predates current air security concerns, the “hub and spoke” design does support for a cleaner separation of various user groups to help ensure good security.
Exercise for the reader: Draw a PAS for MCO. Be sure to note all the interactions between the air side and the land side, and to account for all the inputs and outputs to the airport as a whole. Consider what else might be modularized to make some future airport even more balanced. What are the characteristics of the site on which the airport rests that have allowed for this system design, and that are not necessarily present at the sites of other airports? Why do they matter? Given what you've learned here, what might be done to improve the design of future airports?