"Doug" wrote in message
om...

Go to Alaska, the same airport has TWO id's (or at least they did, not
sure if they've cleared up that mess yet).


K is used to prefix 3-letter airport identifiers only in the 48 contiguous
US states. The letter P is used in the Pacific region; Alaska uses A, F, O,
or P as the second letter of an ICAO identifier, Hawaii uses H. If the
first letter of an Alaskan 3-letter identifier is A, F, O, or P, then the
ICAO identifier can be the normal 3-letter identifier prefixed by P. An
example is Anchorage, the 3-letter identifier is ANC, the ICAO identifier is
PANC. If the first letter of an Alaskan 3-letter identifier is something
other than A, F, O, or P, then the ICAO identifier is usually created by
prefixing the first two letters of the 3-letter identifier by PA, PF, PO, or
PP. An example is Elmendorf, the 3-letter identifier is EDF, the ICAO
identifier is PAED.



Apparently there is the FAA way and the ICAO way and sometimes
they are different. And do you put a K in front of the ones with a
number?


No.



Sometimes, I've seen programs where you do.


Yes, some GPS manufacturers follow that convention, but a proper ICAO
identifier has no numbers.