I do not suppose this has ever been noticed or discussed anywhere before. There are a great many ICAO codes in Eurasia, and particularly in Russia and China, where the last three letters are the same. Some other such airports are scattered around the world. Here goes (what I know), in alphabetical order:

• DBBB: Cotonou, Benin
• DXXX: Lomé, Togo
• HSSS: Khartoum, Sudan
• NVVV: Port-Vila, Vanuatu
• NWWW: Nouméa, New Caledonia
• OIII: Tehran (Mehrabad), Iran
• TFFF: Fort-de-France, Guadeloupe
• UAAA: Almaty, Kazakhstan
• UBBB: Baku, Azerbaijan
• UEEE: Yakutsk, Russia
• UHHH: Khabarovsk, Russia
• UIII: Irkutsk, Russia
• UKKK: Kiev (Zhuliany), Ukraine
• UOOO: Norilsk, Russia
• URRR: Rostov-on-Don, Russia (CLOSED and replaced by URRP)
• USSS: Ekaterinburg, Russia
• UTTT: Tashkent, Uzbekistan
• UWWW: Samara, Russia
• VCCC: Ratmalana, Sri Lanka
• VHHH: Hong Kong, China (SAR)
• VYYY: Yangon, Myanmar
• WAAA: Makassar, Indonesia
• WIII: Jakarta (Soekarno-Hatta), Indonesia
• WSSS: Singapore, Singapore
• ZGGG: Guangzhou, China
• ZHHH: Wuhan, China
• ZLLL: Lanzhou, China
• ZPPP: Kunming, China
• ZSSS: Shanghai (Hongqiao), China
• ZUUU: Chengdu, China
• ZWWW: Ürümqi, China

Special mention to CYYY (Mont-Joli, Canada) and, the king of them all, MMMM (Morelia, Mexico).

A few codes miss by a hair's breadth: for instance GMMN (I have never been able to understand where the 'N' in its IATA code comes from. This is of special importance as this country's flag carrier is joining Oneworld). Furthermore, when Hong Kong is VHHH, Macau could just as well have been VMMM. Why VMMC?

All in all, a very intriguing list. Thoughts?

VTCIE wrote:

Furthermore, when Hong Kong is VHHH, Macau could just as well have been VMMM. Why VMMC?

All in all, a very intriguing list. Thoughts?

Nice list! I'm surprised that pattern is so common given how awkward they'd be over the radio; it's easier to catch a series of differing phonetic letters instead of trying to count three WHISKY in a row.

I always remembered VHHH as Hong Kong Harbour but I doubt that had any official basis.

While all major airports in Germany start with EDD, there isn't an EDDD airport. They could have used it for Dusseldorf, but that became EDDL. Dresden became EDDC.

By the way I found another one: LDDD Zagreb, Croatia.

PatrickZ80 wrote:

While all major airports in Germany start with EDD, there isn't an EDDD airport. They could have used it for Dusseldorf, but that became EDDL. Dresden became EDDC.

Some other countries also follow this system of fixing the middle two letters, like neighbouring Austria, which has LOW*, and Malaysia, which has WMK* (Peninsular), WBK* (Sabah) and WBG* (Sarawak). The big exception is WMSA (Subang Airport).

PatrickZ80 wrote:

By the way I found another one: LDDD Zagreb, Croatia.

That's LDZA. LDDD is apparently the AFTN airport code. Any idea what AFTN is?

Fact: Denpasar had WRRR in the past, but it's WADD now. viewtopic.php?t=768991#p11096883

N.B. Rephrasing my question more clearly: where does the N in CMN (ICAO code: GMMN) come from? This is a simple explanation of my cryptic question in the first post. (It is certain that Royal Air Maroc is joining Oneworld, and announcing it on Wednesday.)

East Texas Regional Airport (Longview, TX), gets its code from the fact that it's in Gregg County: KGGG. Served by AA. That's the only "triple code" assigned to a US airport with commercial service, although there are a couple of GA and military airfields that have triples.

Not related to the OP's question, but I've always liked YSSY for Sydney.

Interesting list and codes. Keep the list going.

There are also some airport codes that start with the same three letters, such as Mexico City (MMMX) .

And there are repeating codes where the first two are the same as the last two, such as EHEH for EIN.

Not entirely related but the ICAO code for Key West begins to spell 'Key West': KEYW

BWIAirport wrote:

Not entirely related but the ICAO code for Key West begins to spell 'Key West': KEYW

That's one of the best, one of the worst has to be Rapid City (KRAP).

While Changi uses WSSS, Seletar Airport (which was meant to start ops in early Dec but hasn't done so due to Malaysian belligerence), is WSSL. Paya Lebar Air Base, which is usually used by VVIPs (e.g. heads of state), is a military base, and has had some very rare SQ diversions, is WSAP.

OP: "Furthermore, when Hong Kong is VHHH, Macau could just as well have been VMMM. Why VMMC?"
It COULD be because Macau airport opened only in 1995 where as HKG [Kai Tak] opened 1925 ie pre ICAO

VTCIE Reply 4: "That's LDZA. LDDD is apparently the AFTN airport code. Any idea what AFTN is?"
AFTN: Aeronautical Fixed Telecommunications Network. See: https://en.wikipedia.org/wiki/Aeronauti ... on_Network, Was originally a telex service linking airlines, airports, regulators & service companies, now an IT network of various forms. Owned by aviation companies [mainly airlines] and run via SITA. See: https://www.sita.aero/about-us

Gemuser

PatrickZ80 wrote:

While all major airports in Germany start with EDD, there isn't an EDDD airport. They could have used it for Dusseldorf, but that became EDDL. Dresden became EDDC.

By the way I found another one: LDDD Zagreb, Croatia.

What about those ICAO LOCIDs I have in my logbook, ETAR, ETAF, ETMN, ETNN and ETAD, all in Germany.

GF

http://gc.kls2.com/airport/MLM

Four of a kind, ladies and gentlemen, read 'em and weep.

Any other quadruples out there?

GalaxyFlyer wrote:

What about those ICAO LOCIDs I have in my logbook, ETAR, ETAF, ETMN, ETNN and ETAD, all in Germany.

GF

Looks like they're all military. In Germany civilian airports start with ED and military airports with ET.

According to Wikipedia, Casablanca Airport was once Nouasseur Air Base, and even today locals call it "Nouaceur" which is the name of the province it is located.
May be that's the reason of the "N" in the ICAO code.

PatrickZ80 wrote:

GalaxyFlyer wrote:

What about those ICAO LOCIDs I have in my logbook, ETAR, ETAF, ETMN, ETNN and ETAD, all in Germany.

GF

Looks like they're all military. In Germany civilian airports start with ED and military airports with ET.

To be precise, before the fall of the Wall, ED airports were West German and ET were East German. After reunification ED got civil airports and ET, military airports.
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SRQKEF wrote:

There are also some airport codes that start with the same three letters, such as Mexico City (MMMX) .

MMMA: Matamaros (MAM)
MMMD: Mérida (MID)
MMML: Mexicali (MXL), the northernmost airport in the country
MMMT: Minatitlán (MTT)
MMMY: Monterrey (MTY)
MMMZ: Mazatlán (MZT)

Of course, there is also this:

PSAatSAN4Ever wrote:

http://gc.kls2.com/airport/MLM

Four of a kind, ladies and gentlemen, read 'em and weep.

Any other quadruples out there?

I have noted this in my first post.

and, the king of them all, MMMM (Morelia, Mexico)

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Coal wrote:

While Changi uses WSSS, Seletar Airport (which was meant to start ops in early Dec but hasn't done so due to Malaysian belligerence), is WSSL. Paya Lebar Air Base, which is usually used by VVIPs (e.g. heads of state), is a military base, and has had some very rare SQ diversions, is WSAP.

Yes. XSL (Seletar) was supposed to have service to SZB, but I don't know what happened. Changi uses WSSS and the smaller Seletar uses WSSL; in contrast, Colombo (Bandaranaike) uses VCBI, while the smaller Ratmalana uses VCCC.
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danvs wrote:

According to Wikipedia, Casablanca Airport was once Nouasseur Air Base, and even today locals call it "Nouaceur" which is the name of the province it is located.
May be that's the reason of the "N" in the ICAO code.

Thank you very much for the help. The 'MN' appears in not only the ICAO code (GMMN) but also the IATA code (CMN).
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Eindhoven wrote:

And there are repeating codes where the first two are the same as the last two, such as EHEH for EIN.

Another example is LJLJ: Ljubljana, Slovenia. Some other little-known examples:
ENEN: Engeløy, Norway
FEFE: Mobaye, C.A.R.

There are also the likes of DFFD (Ouagadougou, Burkina Faso).

This reminds me of the remarkable similarities in Caribbean ICAO codes that begin with T. There are:
TAPA: Anguilla (ANU)
TBPB: Bridgetown (BGI)
TDPD: Dominica (DOM)
TGPG: Pearls, Grenada (closed 1984)
TKPK: Basseterre (SKB)
TLPL: Vieux-Fort (UVF)

TJSJ: San Juan (SJU)
TVSV: Kingstown (SVD), replaced in 2017 by TVSA (also SVD).

TAPA is Antigua, not Anguilla. That is TQPF.