Until 2005 Chicago O’Hare International Airport was the world's busiest airport in terms of passenger numbers, but in that year it lost this position to Hartsfield-Jackson Atlanta International Airport.
However, you can measure the size of an airport in more than 1 way. Other measures are the number of international passengers, the number of operations (take-offs and landings), the volume of freight or a combination of passengers and cargo.
Airports Council International (ACI) released the preliminary top-20 of the world’s busiest airports in 2014.
On the basis of the number of passengers Atlanta is by far the world’s busiest airport with more than 96 million passengers. Beijing is the second and London Heathrow the third largest airport. Chicago O’Hare has dropped to rank 7.
Eight of the largest airports in terms of passenger traffic are located in Asia, 6 in the USA, 5 in Europe, and 1 in the Middle East.
Istanbul is the fastest growing airport with a passenger growth of nearly 11%. As a result, it moved to rank 13 in 2014 from 18 in 2013.
Shanghai’s number of passengers grew 9.5% in 2014 placing it in 19th position, 2 ranks higher than in 2013.