EGLL (or is it LHR) to VHHH (that’s HKG to you)


ICAO codes vs IATA codes
Having worked in Air Traffic Control / Air Traffic Management for 35 years this year, I’m aware that like many industries we have our own language! I think ATC has more TLAs (yes, that’s Three Letter Acronyms) than most.
I would guess that most people would refer to airport names by their full name - in this instance London Heathrow or Hong Kong, (or maybe Chek Lap Kok)…. some people, particularly frequent travellers, but also pilots (and most other areas of aviation) use the three letter IATA (International Air Transport Association) designators. These are the ones found on your suitcase labels that are supposed to prevent them getting lost. They are generally reasonably easy to recognise. For example, the ones for this trip are LHR - London HeathRow, HKG - Hong KonG, and AKL - AucKLand - Pretty straightforward eh?
Not good enough for ATC! In ATC we use the ICAO (International Civil Aviation Organisation) four letter designators. These are divided into geographical areas of the world - which does help you locate the place in question, but invariably (with the exception of North America) also means that you just have to learn the ones you need to know!
Rather than only airports, ICAO codes are used to identify other establishments such as ATC centres, weather stations, and also Flight Information Regions (FIRs) too.
Geographical Areas

The first letter of the ICAO code relates to the region of the world where the unit is situated (like everything there are exceptions!). So for London Heathrow - it’s Europe E , Great Britain G and then two letters that identify the actual station in that area. For Heathrow that is LL - Meaning Heathrow is EGLL (Echo Golf Lima Lima). Generally the major unit in an area has a double letter at the end (the LL in this instance) with smaller units located nearby will have the L but then a different last letter. For example, Blackbushe, a small general aviation airfield is EGLK My understanding is that this scheme originates from the original routings that electronic messages used to take across the AFTN (Aeronautical Fixed Telecommunications Network).
In the example above AFTN messages for EGLK would route via EGLL
North American usage
North American usage seems much easier to understand. Canada and the US just stick their ICAO initial letter in front of the IATA code! So JFK John F Kennedy in New York becomes KJFK
Our trip
This trip of ours takes us from EGLL to VHHH and then on to NZAA!