Why Is There an X in Some Airport Names? (& Some Funny Codes)

There’s a fascinating story about airport location codes. Yes, really, it’s interesting and there’s more to it than you might initially think!

In this article, I’m going to give some background to how airport codes are designated, and then focus on a particular peculiarity – the presence of the letter ‘X’ in airport codes. Finally, I’ll add a little fun and list out some of the weirder airport codes.

IATA vs. ICAO Airport Codes

Airport codes are designated by either three or four-letter codes. The three-letter codes are allocated by the International Air Transport Association (IATA), and the four-letter codes by the International Civil Aviation Organization (ICAO).

The ICAO codes are used within the aviation industry for operational purposes such as airport traffic control and flight planning. In this article, I’m going to talk only about IATA’s three-letter codes which are more commonly used for travel itinerary planning and airline ticketing.

How Are 3-Letter Airport Codes Assigned?

Many airport codes make perfect sense. Take JFK and LGA as examples. Everyone knows that JFK stands for John F. Kennedy International Airport, and LGA stands for La Guardia Airport in New York, right?

Some codes are clearly shortened versions of the name of the city they serve. It’s easy to work out that MAN is the airport for Manchester, SEA for Seattle, BOS for Boston, MEX for Mexico City, LUX for Luxembourg, and SIN for Singapore.

In some cases, the codes still reflect a historic name for a city. For example, BOM is the airport for Mumbai, previously known as Bombay, CAN is the airport for Guangzhou in China, previously known as Canton, and SGN is the code for the airport serving Ho Chi Minh City in Vietnam, previously known as Saigon.

However, there are some airport codes that are a bit of a mystery, and you often need to look back at the history of the airport to understand its IATA code. Take, for example, Orlando International Airport (MCO). Before this airport became the gateway to Florida’s multiple theme parks, it was a United States Air Force (USAF) base named McCoy Air Force Base.

Also, did you ever wonder why Newark Liberty International Airport has the code EWR? Well, again there’s some interesting history here. When the US codes changed from two-letter to three-letter codes the US Navy reserved the letter ‘N’ for the start of its air bases. So, Newark airport had to use a code made up of other letters and they ended up using NEWaRk. Kansas City International Airport’s code is MCI; the reason for this is that the airport was previously named Mid-Continent International Airport.

Next, let’s now explore why there are so many IATA airport codes that contain the letter ‘X.’

The Reason There Is an ‘X’ in Some Airport Codes Is Obvious

Of course, it makes perfect sense for some airports to have an X in their three-letter code. We won’t dwell on this because we want to explore those airports where, at first glance, an ‘X’ doesn’t appear to make sense. But here are a few examples where it does make sense:

• Alexandroupolis Airport, Greece (AXD);
• Alexandria International Airport, Louisiana, USA (AEX);
• Henry E. Rohlsen Airport, Christiansted St. Croix, Virgin Islands (STX); and
• Araxá Airport, Brazil (AAX).

And there are the examples given previously in this article – LUX and MEX.

Letter ‘X’ at the End of the IATA Code of US Airports

To answer the question ‘Why is there an X in some airport codes?’ we need to look into some history. In the USA there are many airport codes where ‘X’ is in the final letter.

Originally airports in the USA were designated with a two-letter code. These codes were the same as the city codes used by the US National Weather Services, and at the time it was never foreseen that there would be so many airports in the future that three-letter codes would be needed to give more code combinations.

So, to demonstrate this, we can look at the previous and current airport codes for Los Angeles International Airport – originally LA and now LAX, Portland International Airport – originally PD, and now PDX, Phoenix Skyharbor International Airport also fits this pattern – originally PH, and now PHX – but even so, PHX makes a lot of sense anyway.

Let’s take a look at other ways that, and why, the letter ‘X’ is incorporated into airport codes.

Other Uses of the Letter ‘X’ in the IATA Code

The answer here often lies in the fact that where there are similar city names, or more particularly, where city names begin in a similar way, the airport code may already be taken and the letter ‘X’ basically acts as a filler.

There are many examples around the world where this has happened, probably hundreds, demonstrating the need for IATA to use three-letter codes to increase the number of available airport codes. Here are some examples to explain this:

• Dubai International Airport, Dubai, United Arab Emirates (DXB) ideally would have the three-letter code DUB, but this code was already taken by Dublin International Airport, so for Dubai, the U was substituted with the filler X to give DXB.
• The code for Birmingham International Airport in the UK is BHX. This is because BHM was already taken by Birmingham Airport in Alabama, USA, when BHX was designated.
• The code for Marion Downs Airport in Queensland, Australia is MXD. This is because MAD was already taken by Madrid Barajas International Airport in Spain, when MXD was designated.
• The code for Granada Airport in Spain is GRX. Presumably, the airport wanted to use the code GRA already allocated to Gamarra Airport in Colombia.
• The code for Araguaína Airport in Brazil is AUX. The code AUA was already allocated to Queen Beatrix International Airport in Aruba.
• The code for RAF Benson in the UK is BEX. The code BEN would have been more appropriate, but Benina International Airport in Libya uses this code.

The Funny Side of Airport Codes

I’m going to finish this article with a look at the funny side of airport codes. Some airport codes are downright amusing (or perhaps unfortunate). How would you feel about flying into the following airports?

• PEE (Bolshoye Savino Airport, Perm, Russia)
• POO (Poco De Caldas Airport, Brazil)
• ROT (Rotorua, New Zealand)
• BUM (Butler Airport, Missouri, USA)
• BAD (Barksdale Air Force Base, Louisiana, USA)
• DIE (Arrachart, Madagascar)
• FAT (Fresno, California, USA)
• GAG (Gage, Oklahoma)
• GRR (Gerald R. Ford International Airport, Grand Rapids, Michigan, USA)
• LOL (Derby Field, Lovelock, Nevada, USA)
• OMG (Omega Airport in Namibia)
• EEK, (Eek, Alaska, USA)
• SAD (Safford, Arizona, USA)
• WOW (Willow, Alaska, USA)
• DUM (Dumai, Indonesia)
• HIP (Headingly, Australia)
• HOT (Hot Springs, Arkansas, USA)
• BOO (Bodo Airport, Norway)

And, not forgetting SUX (Sioux City, Iowa). Originally the SUX airport operator objected to its unfortunate designation, but soon came to embrace it, and now does pretty well from its ‘flySUX’ merchandise!

Summary

Some IATA three-letter airport codes are immediately obvious and it’s easy to tell which city the airport serves. But some are harder to work out and you might need to know the history of the airport and any names it might have, or had, to work it out, especially if the airport was named after someone famous or a local politician.

The letter ‘X’ is very common in IATA airport codes. Sometimes it makes sense because the city name contains the letter ‘X’ – think MEX for Mexico City. But, more often than not the letter ‘X’ is a filler or replacement letter. This is usually for one of two reasons, as follows:

• The change from two-letter to three-letter codes in the 1940s meant that the letter ‘X’ was added at the end to complete the three-letter code – think LAX for Los Angeles International Airport
• The obvious three-letter code for an airport might already be allocated and so the letter X is used as a replacement – think BHX for Birmingham Airport in the UK (the code BHM was already taken)

Whilst, this is all very serious, there is an irreverent side to airport codes too, I hope you found this article informative as well as fun!