Source: adapted from R. Baseler (2003) "Market Outlook for Air Travel:
A Global Perspective", 2nd Annual MIT Airline Industry
(Detailed PDF map)
Air Hubs and Market Fragmentation
Before deregulation and Open Skies agreements only a few city-pairs
could be serviced. The unavailability of lower capacity aircrafts for
long ranges also meant that only the largest city-pairs could be serviced.
Deregulation and the introduction of smaller wide-body long range aircrafts
such as the Boeing 767 (about 250 passengers), the Boeing 777 (about
350 passengers), and the Airbus A330 (about 300 passengers) permitted
a wider range of city-pairs to be serviced and involving cities of lesser
size. The fact that Chicago became a hub enabled the consolidation of
a larger number of passengers bound to various European cities.