But which begs the question. Why are those airports slot limited? Prior to the introduction of the 747 there weren't any aircraft with the range for Dallas to Tokyo or Dallas to London flights. People from the middle of the country wanting to travel to Europe tended to fly first to JFK to catch another plane to a major hub on the other side of the Altantic or to LAX or Seattle to go to destinations in the Pacific. Many of the people flying to Tokyo were actually continuing on to other destinations.
With 180 minute and longer ETOPS, and longer ranged smaller planes, someone flying from Dallas or Houston can fly directly to Seoul, Honk Kong, Bejing or other Asian destinations without first flying through two hub airports first. This decreases demand for 747 or A380s flying from LAX or SEA to NRT.
This process is also happening in the UK with charter operators moving operations out of London airports like Heathrow and Gatwick. They are flying directly to tourist destinations like Cancun and Orlando and various cities in Europe. This eliminates traffic on London to Mexico City and London to Miami routes.
In Europe and much of Asia, they have no more space to build the type of expansive airport that can support large numbers of takeoffs and landings per day. As a result, the only way to increase capacity is to fly larger planes, hence the reason why the medium-range version of the 777-300 has sold very well in the Asian market and why the majority of Asian airlines are buying the A380-800. Here in the USA, we have a very large number of airports with commercial airline service operating point-to-point flights, hence the reason for the success of Southwest Airlines, JetBlue Airways and AirTran.
I wonder how much of that decreases traffic on the trunk routes and how much of it expands the overall market by bringing cheap tourists to destinations they wouldn't have considered before. I think that a lot of the package trips to Cancun and the Dominican Republican from Europe are tapping into new markets by attracting people who would have otherwise gone to Ibiza or the Canaries on a similarly priced package, or maybe nowhere at all.
The answer is simple, with the notable slight exception of Japan (e.g. Osaka), Asian countries don't have Dallases, Denvers or Detroits. Such airports do not exist there. In Asia, airports are either behemoths, or, places that can barely take a 737.
Narita is slot limited because it has just one runway, they have tried for years to get a second one, but the farmers in the area have balked. Great airport though, one of the few big ones that still has an outside observation deck. Heathrow is slotted because of space, gates and number of flights, its a big airport and has lots of movements.