Does anyone know how the airport code naming scheme works in USA?I ran into an airport called McClure or Troy McClure.However it has two codes PN21 and 75N and both belong to the same airport (airnav.com).Which is the "better" or newer code?Are the three letter N codes being phased out?This has nothing to do with IATA or ICAO codes - I know about those.ThanksPaul

>This has nothing to do with IATA or ICAO codes - I know about>those.Actually it has everything to do with ICAO. I don't know the actual year about but since then the US has been standardizing to the world format of aviation. This was pretty much everything from NOTAMs, weather, to airport identifiers. Each world region has a different prefix in the four letter identifiers. Your example if PN21 that is either an Alaskan airport or a Pacific Island airport. As time goes on the US is slowly trying to transition the airport identifiers over that represent the airport in either name or location by three letters plus the prefix.

The following is from FAA Order JO 7350.7X:1-2-7. ASSIGNMENT SYSTEMa. Three-letter identifiers are assigned as radiocall signs to aeronautical navigation aids; toairports with a manned air traffic control facilityor navigational aid within airport boundary; toairports that receive scheduled route air carrier ormilitary airlift service, and to airports designatedby the U.S. Customs Service as Airports of Entry.Some of these identifiers are assigned to certainaviation weather reporting stations.d. Most one-letter, two-number identifiers areassigned to public-use landing facilities within theUnited States and its jurisdictions, which do notmeet the requirements for identifiers in the threeletterseries. Some of these identifiers are alsoassigned to aviation weather reporting stations.1. One-letter, two-number identifiers arekeyed by the alphabetical letter. The letter mayappear in the first, middle or last position in thecombination of three characters. When the lettersignifies an Air Traffic Control Center

Thanks Scott

You mentioned VG for Virginia, but I have many private use airports in my logbook that begin with VA or end in VA.

That's not me, it's the FAA, but I think what it is saying is that the 2 letters are either the normal postal abbreviation (VA for Virginia), or the "supplemental abbreviation" (VG for Virginia).scott s..