This is the first field I looked at and it seems that this is only available in the original out of date supplied data from VAM. For my initial entry for this I set a default of 'airport' which makes some sense. However later on providing i have enough data that matches back to the VAM data I can update this to their values such as 'small_airport' , 'large_airport' etc. This is one of the more difficult fields to get the correct data from as many airports change their name and sometimes they change the ICAO code if available. Remember my test case of Jan Smuts Airport in South Africa that was FAJS becoming OR Tambo and FAOR. I needed a set of data that was correct with the names of Airports associated with the ICAO code if possible. It so happens if you are careful you can get a free set of data using an API KEY from a real world website in fact it is ICAO themselves https://www.icao.int/safety/iStars/Pages/API-Data-Service.aspx For free...