Just thought i would educate the ill informed west coast
Busiest International Airport
London Heathrow handles the most international passengers (as opposed to passengers on domestic flights, which make up the majority of traffic at US airports). On an overall scale, Heathrow ranks third behind Atlanta and Chicago.
Busiest City (all airports)
When the flights from all airports in a city are combined, London is the busiest aviation centre in the world.
Only London, Tokyo and New York have two airports in the top 30 worldwide.
Combining New York's JFK (29 943 084) and Newark (29 202 654 ) still does not reach the same level as London Heathrow. Despite being the major international gateway for Japan, Tokyo Narita (28 883 606) is overshadowed by the mainly domestic Haneda (61 079 478). This puts Tokyo on a relatively even keel with Heathrow (63 338 641) and Gatwick (29 628 423).
When Stansted (18 750 000), Luton (6 500 000), and London City (1 500 000) are added on top, London handles a total of almost 120 million passengers annually.
Source: World airports Council , BAA, Luton Airport, London City Airport
As you can quite clearly see, the LTMA is by far the busiest in the world and all within such a confined area. On the other hand o'hare is pretty much isolated!!! on its own