Ever since the United States aviation market shifted from the point to point transport model, airlines have made hubs, and destroyed them. The hub and spoke model is " a system of connections arranged like a chariot wheel, in which all traffic moves along spokes connected to the hub at the center," as per an official definition. The hub and spoke model was pioneered by Delta in 1955 at Atlanta (no surprise there), then after airline de-regulation in 1978, everybody else followed.
How does the hub and spoke model work? Well, look at it this way. Lets say that an airline operates a 50 seat jet between St. Louis, and Aspen. Well, most likely, only 10-15 of those people are actually going to Aspen. But if five people from Atlanta, Boston, Hartford, Detroit, and Pittsburgh respectively get on that plane, then suddenly it could be full. And vice versa, maybe there aren't enough people to fill a plane from Aspen to any of those places.
Here is a model depicting the phenomenon:
So to start off, I'd like to define what exactly makes an airport a hub for an airline
To be a hub, under my definition, an airline's operation at an airport must fit one of the following categories
- They hold a marketshare of at least 45% at an airport with more than 5 million enplanements in 2008.
- They operate at least 150 daily flights at the airport, when combined with their regional partner
- They enplane at least 5.5 million passengers a year at the airport
Under those definitions, here are airline hubs in 1990, and in 2010
1990
America West:
Las Vegas
Phoenix
American:
Dallas Fort Worth
Raleigh- Durham
Nashville
Chicago O'hare
San Jose
Braniff (2):
Kansas City
Continental:
Cleveland
Denver
Houston
Newark
Delta Airlines:
Boston
Cincinnati
Dallas Fort Worth
Atlanta
Orlando
Salt Lake City
Los Angeles
Eastern Airlines:
Atlanta
Miami
Midway Airlines:
Chicago Midway
Midwest Airlines:
Milwaukee
Pan Am:
New York- JFK
Miami
TWA:
St. Louis
New York-JFK
United:
Denver
Chicago O'hare
Los Angeles
Tokyo-Narita
San Francisco
Washington-Dulles
US Airways:
Pittsburgh
Baltimore-Washington
Philadelphia
Charlotte-Douglas
2010
Alaska:
Seattle Tacoma
Air Tran:
Atlanta
Orlando
American Airlines:
Dallas Fort-Worth
Miami
Chicago O'hare
New York-JFK
New York- La Guardia
Los Angeles
Continental Airlines:
Cleveland
Newark
Houston Intercontinental
Delta Airlines:
Atlanta
Cincinnati
Detroit-Metro
Minneapolis- St. Paul
Salt Lake City
Memphis
Tokyo-Narita
Frontier Airlines:
Denver
Milwaukee
JetBlue Airways:
New York- JFK
Southwest Airlines:
Las Vegas
Los Angeles
Baltimore-Washington
Chicago- Midway
Denver
Orlando
Phoenix
San Diego
Tampa
United Airlines:
San Francisco
Denver
Los Angeles
Chicago O'hare
Washington-Dulles
US Airways:
Philadelphia
Charlotte-Douglas
Phoenix
Washington-Reagan
Original Image Credit: http://www.delta.com/planning_reservations/plan_flight/aircraft_types_layout/crj-200/- CRJ layout