Sydney s/h,
Sorry if I'm telling you some of the abbreviations you already know, but here goes:
HNL = Honolulu
You know what DVT and and ER are...
LAX = Los Angeles
AKL = Auckland
Wx = weather
rwy XW = runway crosswind
CHC = Christchurch
NFFN = Nadi, Fiji
PHNL = Honolulu
NZAA = Auckland
You notice that airfields can be referred to as either a 3- or 4-letter identifier (PHNL = HNL = Honolulu).
The 3-letter identifier is known as the IATA (International Air Transport Association) airport code. It is commonly used in airline-type applications like crew rosters, airline timetables, bag tags and so on. Military organisations are less likely to use these codes.
The 4-letter code is the ICAO (International Civil Aviation Organisation) code, and is used more in operational-type functions like weather, NOTAMs (Notices to Airman), and flight planning. ICAO codes are used universally by all aviation organisations: airline, military, government etc.
They aren't always easy to associate... don't be fooled by the similarity between PHNL and HNL. Perth = YPPH = PTH, London Heathrow = EGLL = LHR.
The IATA codes are sometimes difficult to pin to an airport without some usable directory or database. Sometimes they resemble the city name (Sydney = SYD, Melbourne = MEL), but sometimes are less similar (Vancouver = YVR).
The ICAO codes are more global in their nature. It isn't too hard to pick the region, but harder to pinpoint. For example codes starting with:
K*** are mostly in USA
C*** Canada
P*** Pacific USA (eg Hawaii, Alaska)
N*** Pacific (eg Fiji, Samoa, Tahiti, New Zealand, Vanuatu, New Caledonia)
Y*** Australia
A*** Papua New Guinea/Solomon Islands
W*** South East Asia
E*** Europe
F*** Africa (I think)
Additionally, sub regions can be identified, for example:
WM** = South East Asia (Malaysia)
WI** = South East Asia (Indonesia)
EG** = Europe (Great Britain)
ED** = Europe (Deutschland - Germany)
NZ** = Pacific (New Zealand)
NF** = Pacific (Fiji)
Of course, there are many confusing exceptions...
A quick Google search revealed this site :
http://www.activitae.com/airbase/icaoCode.htm
It is for decoding or encoding ICAO codes. Search for "IATA Decode" and you will find many similar products...
Hope this helps...
VI
PS - Sorry to all for massive bracket creep... this thread had quietened down anyway.