We want to be able to also use the ICAO codes for searching flights and airports, because many smaller airports do not have a IATA code as they don't serve the general public airliners or doesn't have internet connection to their flight data.
The first letter are according to this map:

We can either download the entire ICAO database or check if there is a f24 query for this.
There airports with no IATA, has the \N in the field for IATA, and sorted on ICAO.
There are 4701 airports without an IATA code!
We want to be able to also use the ICAO codes for searching flights and airports, because many smaller airports do not have a IATA code as they don't serve the general public airliners or doesn't have internet connection to their flight data.
The first letter are according to this map:
We can either download the entire ICAO database or check if there is a f24 query for this.
There airports with no IATA, has the
\Nin the field for IATA, and sorted on ICAO.There are 4701 airports without an IATA code!