Many large metropoles around the world have multiple major airports with commercial airline service:

* London, famously, has *six* ([EGLL](https://en.wikipedia.org/wiki/Heathrow_Airport), [EGLC](https://en.wikipedia.org/wiki/London_City_Airport), [EGKK](https://en.wikipedia.org/wiki/Gatwick_Airport), [EGSS](https://en.wikipedia.org/wiki/London_Stansted_Airport), [EGGW](https://en.wikipedia.org/wiki/Luton_Airport), [EGMC](https://en.wikipedia.org/wiki/London_Southend_Airport)),1 although the latter four are far enough away to seriously stretch the bounds of “serving London”.
* Paris has two ([LFPG](https://en.wikipedia.org/wiki/Charles_de_Gaulle_Airport) and [LFPO](https://en.wikipedia.org/wiki/Orly_Airport)).2
* Rome has two ([LIRF](https://en.wikipedia.org/wiki/Leonardo_da_Vinci%E2%80%93Fiumicino_Airport) and [LIRA](https://en.wikipedia.org/wiki/Ciampino%E2%80%93G._B._Pastine_International_Airport)).
* Moscow (the one in *Матушка Россия*, not [the one in Idaho](https://en.wikipedia.org/wiki/Moscow,_Idaho)3) has four ([UUDD](https://en.wikipedia.org/wiki/Moscow_Domodedovo_Airport), [UUEE](https://en.wikipedia.org/wiki/Sheremetyevo_International_Airport), [UUWW](https://en.wikipedia.org/wiki/Vnukovo_International_Airport), [UUBW](https://en.wikipedia.org/wiki/Zhukovsky_International_Airport)).
* Istanbul has three ([LTFM](https://en.wikipedia.org/wiki/Istanbul_Airport), [LTFJ](https://en.wikipedia.org/wiki/Istanbul_Sabiha_G%C3%B6k%C3%A7en_International_Airport), [LTBA](https://en.wikipedia.org/wiki/Istanbul_Atat%C3%BCrk_Airport) [cargo-only]).
* Beijing has two ([ZBAA](https://en.wikipedia.org/wiki/Beijing_Capital_International_Airport) and [ZBAD](https://en.wikipedia.org/wiki/Beijing_Daxing_International_Airport)).
* Shanghai has two ([ZSPD](https://en.wikipedia.org/wiki/Shanghai_Pudong_International_Airport) and [ZSSS](https://en.wikipedia.org/wiki/Shanghai_Hongqiao_International_Airport)).
* Bangkok has two ([VTBS](https://en.wikipedia.org/wiki/Suvarnabhumi_Airport) and [VTBD](https://en.wikipedia.org/wiki/Don_Mueang_International_Airport)).
* Seoul has two ([RKSI](https://en.wikipedia.org/wiki/Incheon_International_Airport) and [RKSS](https://en.wikipedia.org/wiki/Gimpo_International_Airport)).
* Tokyo has two ([RJAA](https://en.wikipedia.org/wiki/Narita_International_Airport) and [RJTT](https://en.wikipedia.org/wiki/Haneda_Airport)).

In some of these cases (London, Istanbul, Beijing, Seoul), a new airport(s) has been opened explicitly to relieve the crush that existed previously, and/or preexisting satellite airports have been extensively touted as destinations in an effort to take pressure off overloaded primaries; in many to most of these cases, the existence of multiple airports has allowed particular categories of service to be concentrated at particular airports (for instance, one airport handles long-distance international flights while another handles domestic and regional flights, or one airport handles traditional carriers while another handles low-cost carriers, or [in Istanbul’s case] one airport is dedicated to cargo flights).

U.S. cities, like their international compatriots, frequently have multiple major airports.4 *Unlike* their international compatriots, however, U.S. cities show a pronounced tendency to try as hard as possible to squeeze everything into One Big Airport, with airlines often being kicked out of their homes at preexisting downtown airports and forced over to the One Big Airport (often an hour’s drive or more from the city it claims to serve):

* New York has three major airports ([KJFK](https://en.wikipedia.org/wiki/John_F._Kennedy_International_Airport), [KLGA](https://en.wikipedia.org/wiki/LaGuardia_Airport), [KEWR](https://en.wikipedia.org/wiki/Newark_Liberty_International_Airport));5 of these, KLGA, despite being the most centrally located, has been consistently discriminated against in favour of the Two Big Airports (KJFK and KEWR), being almost entirely barred to flights to or from destinations outside the eastern half of the United States, and *completely* barred to flights operated by non-North-American airlines.6
* Chicago has two major airports ([KORD](https://en.wikipedia.org/wiki/O%E2%80%99Hare_International_Airport) and [KMDW](https://en.wikipedia.org/wiki/Midway_International_Airport));7 despite KMDW’s closer-to-downtown location, the vast majority of traffic goes through KORD, with [only one airline](https://en.wikipedia.org/wiki/Southwest_Airlines) having more than a token presence at KMDW (that one airline accounts for over *95 percent* of all passengers using the airport).
* Dallas/Fort Worth has two major airports ([KDFW](https://en.wikipedia.org/wiki/Dallas/Fort_Worth_International_Airport) and [KDAL](https://en.wikipedia.org/wiki/Dallas_Love_Field)); almost all traffic (again except for essentially [just one airline](https://en.wikipedia.org/wiki/Southwest_Airlines)) uses KDFW, which is centrally located for neither city. In fact, for many years, airlines were *[barred by federal law](https://en.wikipedia.org/wiki/Wright_Amendment)* from operating full-size flights to or from airports not located in Texas or a Texas-neighbouring state out of *any Dallas/Fort Worth airport other than KDFW*,8 in a deliberate attempt to force everyone to use KDFW; this nearly caused the end of airline operations at the much-more-Dallas-convenient KDAL (which was only saved following a lengthy court battle), *did*, in fact, spell the doom for what was then Fort Worth’s main airport ([KGSW](https://en.wikipedia.org/wiki/Greater_Southwest_International_Airport), which was used solely for airline training flights after 1969, closed entirely in 1974, and almost completely razed in the 1980s and 1990s), and prevented [KFTW](https://en.wikipedia.org/wiki/Fort_Worth_Meacham_International_Airport), very close to downtown Fort Worth, from ever becoming successful as a commercial airport.
* Kansas City has two major airports ([KMCI](https://en.wikipedia.org/wiki/Kansas_City_International_Airport) and [KMKC](https://en.wikipedia.org/wiki/Charles_B._Wheeler_Downtown_Airport)); nearly all airline traffic goes through the One Big Airport (KMCI), located far from the city, while the centrally-located KMKC sees only limited cargo service.

(Washington, with two major airports [[KIAD](https://en.wikipedia.org/wiki/Dulles_International_Airport) and [KDCA](https://en.wikipedia.org/wiki/Ronald_Reagan_Washington_National_Airport)], is a rare exception, and, even here, they tried [albeit incompletely successfully] to shoehorn everyone into One Big Airport; KDCA, located almost directly across the Potomac from downtown Washington, sees approximately the same level of service as KIAD, despite the former being restricted [with only a few exceptions] to flights no longer than approximately 2000 kilometers [in an effort to force flights to use KIAD, located nearly 50 kilometers away from the city].) 

Why do U.S. cities have so much of a tendency to try to shoehorn everyone and everything into One Big Airport (or, in giant New York’s case, Two Big Airports), rather than spreading out the load between multiple smaller airports?

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1: Two others ([EGKB](https://en.wikipedia.org/wiki/London_Biggin_Hill_Airport) and [EGWU](https://en.wikipedia.org/wiki/RAF_Northolt)) are kept barred to airline service due to selfish NIMBYs.

2: A third, [LFPB](https://en.wikipedia.org/wiki/Paris%E2%80%93Le_Bourget_Airport), was closed to commercial traffic in 1980 (no reason given, but I’m suspecting it’s the damn NIMBYs again).

3: [Which is itself served by an airport!](https://en.wikipedia.org/wiki/Pullman%E2%80%93Moscow_Regional_Airport)

4: Possibly even *more* frequently, given the quintessentially American love of aviation.

5: A fourth airport, [KHPN](https://en.wikipedia.org/wiki/Westchester_County_Airport), sees some airline service but is handicapped by draconian passenger-volume limits (NIMBYs again) that keep it far below its full potential, while a fifth, [KTEB](https://en.wikipedia.org/wiki/Teterboro_Airport), is completely barred to commercial service via NIMBY-imposed weight limits.

6: In fact, when KJFK (known at the time as KIDL) opened, the European airlines that had, until then, been happily resident at KLGA were forcibly evicted to the new, far-away airport through the cancellation of their permits to operate from KLGA.

7: A third airport, [KCGX](https://en.wikipedia.org/wiki/Meigs_Field), located right on the downtown waterfront, was forcibly closed by the mayor of Chicago in 2003 because he didn’t like it.

8: These restrictions were loosened considerably in 2006, and finally repealed entirely in 2014.