What happens if a code appears in several databases?
The databases have been merged into a single database which attempts to use the “best” data. Because of its greater precision and trustworthiness, the FAA data is favored for a given airport. However, while the FAA ensures that any airport with both an FAA and IATA code has the same code in both registries, it does not otherwise avoid conflicts. For example, CBG is assigned to Cambridge, Minnesota, while IATA uses the same code for Cambridge, England. To resolve this ambiguity, the IATA-listed airport is used if the latitude and longitude are not both within a few degrees of the FAA location. Presumably an IATA-listed airport will be more interesting for great circle routes than a small US airport.
