The ranking is based on a comparison of the number of scheduled connections with the number of destinations served.
Delta uses its Atlanta hub as a connecting point to and from places around the Southeast and for international connections to Europe, Latin America and other regions. It has smaller hubs in cities such as Minneapolis/St. Paul and Salt Lake City for other passengers connecting across the country.
According to the report, there are 63,466 possible connections passengers could make at Hartsfield-Jackson on the busiest day in 2019, with Delta operating 79 percent of flights.
Southwest Airlines, the second-largest carrier in Atlanta, focuses more on travelers going to and from Atlanta and less on connections than a traditional hub carrier might.
Globally, O'Hare ranked third for international connectivity and Hartsfield-Jackson ranked 8th. In the top position for international connectivity was London Heathrow, followed by Frankfurt.