When the Boeing 707 entered service, less than a dozen of the world's big cities had airports that could accept it with full payload-range. After 30 years, they do not seem to be entirely able to cope with the 747s. Every time I fly on a 400-seat Boeing 747, I board or disembark through a single door. That is only the problem on the ground. The air space around the airports is so congested, and the access for the aircraft at the airports is so limited, that almost all the world's big intercontinental traffic hubs have run out of room.
Traffic is dispersed to satellite or partner airports.
New York now depends on three major and three other airports. London has four, and two secondary ones, including Southend. The air traffic control problem in many of these places has already reached crisis level. Problems for New Airport Setting In the United States, only Dallas and Denver have 21st century airports. Airliner approach and departure separation is restricted by forces beyond ATC's control.