Each airport is assigned a three-letter abbreviation, and each airline
has a two character (letters and numbers are used) abbreviation.
Regular readers to the group recognize an amazingly large number
of these codes, and regular posters use the codes liberally in their 
postings.  

As a rule, you should limit the number of airport/airline codes that you
use in your postings.  If you wish to use a code that is not widely
understood, then define the code when you first use it.  For example,
instead of:

   RG will begin non-stop service between JFK and GPS on July 13th.  The
   flight will depart JFK at 3:00pm and arrive GPS at 3:02pm.

you should say:

   Varig (RG) will begin non-stop service between JFK and the Galapagos
   Islands (GPS) on July 13th.  The flight will depart JFK at 3:00pm and 
   arrive GPS at 3:02pm.

Note that JFK (New York's Kennedy airport) is a common enough
abbreviation to probably not need explanation.

The International Air Transport Association (IATA) provides a search
engine for locating airports by three-letter code or by city name:
   http://www.iata.org/codes/
The Airport Search Engine is a bit more powerful.  It lets you search
for airports by IATA abbreviation, city, or country:
   http://www.uni-karlsruhe.de/~un9v/atm/ase.html

You can search for airline (two-letter and three-letter) codes at the 
IATA web site.
   http://www.iata.org/members.htm
Another list of the most common airline codes is available 
at the following URL:
   http://www.flifo.com/aircodeindex.html