Some airports, like Paris-Orly, New York-LaGuardia, and Washington National are slot controlled, and your airline must have slots for the airport in order to fly flights out of there. Take for example DCA
; everytime any slots come open, everybody who either wants to start DCA
service or wants to add additional flights try to get them. The FAA allots those slots to whoever they think deserves them (usually goes to an airline that will add service to a new city from DCA
, or will open up competition on a route). LGA
slots have been allotted by the government and by lottery.
Another reason why airlines don't fly into certain airports is gate space. If your airline wants to fly into an airport at certain times of the day and there are no available gates for that time, you can't fly into there. ATL
is one airport that is practically maxed out gate-wise at certain times of the day even with the shared gates on Concourse D; so unless you can get another airline to handle your flights (like Hooters Air does @ ATL
handling their flights and the flights are going out of Concourse B), you're S.O.L.