Ed,
Thanks to Ward I learned something in his post.
Oops ... I did something valuable? <swallow>
Well, some clarification.
The IATA-codes are issued by the International Air Transport Association.
It's the trade association for the world's airlines, some 370 with varrying numbers. But not all carriers are a member. It sets technical air-safety standards and assigns the 3-letter airport codes used in reservation systems. One of the problems here is that it allows for a theoretical maximum of 17,576 airports, but in reality that is significantly less as certain combinations are not used.
The International Civil Aviation Organization (ICAO) is one of the UN agencies that manages the administration and governance of the Convention of Chicago (1948, I think, which structured world aviation). It uses 4-character codes where the firstone is a global locator, the 2nd the country, and the 2 remaining a 2-character airport code withing that country. It is less flexible than the IATA-code as "K" is the global locater for the USA and "C" for Canada supplemented by the IATA-code. So you have KJFK for Kennedy airport, KLAX for Los Angeles, CYYC for Calgary, CYYZ for Toronto etc ... also re: the second position there would only be 26 countries in the world, so that doesn't work either.
There's also a third code possible, the "WMO" ... World Meteorological Organisation if the airport has a weather station (not all airports do). The code consists of 5 digits ...the first digit gives the region: 0 to 1 for Europe, 2 to 3 for Russia, 4 for Asia, 5 for the Far East, 6 for Africa, 7 for North America, 8 for South America and Antarctica, and 9 for the Pacific.
So for example 72295 is the WMO-code for LAX-airport, 03772 for London Heathrow, Frankfurt is 10637, Beijing (PEK) is 54511, Johannesburg is 68368, Sydney is 94767 ... and so on.
\%/@rd
--- DB4 - 20230201
* Origin: AVIATION ECHO HQ (2:292/854)