Why would you want to look them up? If a poster wants to be understood, he or she will write out the name of the airport. If instead the intent is to appear "in the know" or cool or to communicate to a select few, acronyms are used.

I have been doing this miles thing for more than a few years, and I love this forum as as one of my major sources of information. But if I don't understand the acronyms, I assume the post is not meant for me anyway, and just go onto the next.