RyanairGuru wrote:it is the FAA identifier with a K in front
Except, it must be noted, that the K is the ICAO prefix for the contiguous United States only.
There is also the P code range to consider:
PA USA (Alaska) (also PF, PO and PP)
PB USA (Baker Island)
PC Kiribati (Canton Airfield, Phoenix Islands)
PF USA (Alaska) (also PA, PO and PP)
PG USA (Guam, Northern Mariana Islands)
PH USA (Hawaii)
PJ USA (Johnston Atoll)
PK Marshall Islands
PL Kiribati (Line Islands)
PM USA (Midway Island)
PO USA (Alaska) (also PA, PF and PP)
PP USA (Alaska) (also PA, PF and PO)
PT Federated States of Micronesia, Palau
PW USA (Wake Island)
Doesn't stop people dropping KHNL into posts though, or even (one time that I saw) KPHNL, but it means that all ICAO codes for these areas cannot match the prefix+IATA/FAA general equivalency unless the second letter of the ICAO prefix is the first letter of the IATA or FAA code... so Kahului, for example, has OGG as its FAA and IATA codes but is ICAO coded PHOG.