It is often heard that Atlanta’s Hartsfield International Airport is the busiest airport in the world. On an individual airport basis, that is correct. But when you calculate the total air passengers passing through each market (single airport or multiple-airport), the data shows Atlanta is not even close to the busiest air passenger market in the world, nor is it even the busiest in the United States. Instead, those designations go to Greater London and New York City respectively. In fact, Atlanta’s air passenger traffic would have to increase by approximately 50 percent to reach the total air passenger traffic flying in and out of Greater London. Below is the 2011 data for each of the 25 busiest air travel markets as compiled from the resources listed at the end of the post.