World's busiest airport

The following airports have variously made claims (or had made claims for them).

• O'Hare International Airport, Chicago, USA - Largest number of passengers annually ( pre-1998 , 2003-date) - Most arrivals and departures annually (pre-1998),(2001-)
• William_B._Hartsfield_International_Airport, Atlanta, USA - Largest number of passengers annually (1998-2003) - Most arrivals and departures annually (1999-2000)
• Heathrow Airport, London, UK - Largest number of international passengers annually
• Frankfurt International Airport, Frankfurt, Germany - Most international destinations served.
• Memphis International Airport[?], Memphis, USA (home of FedEx) - Most cargo traffic by volume annually

A 'passenger' is typically described as someone who arrives in, departs from or transfers through the airport on a given day