Several months ago there was a thread on airport codes. I think it started out something like "why is O'Hare's code ORD?" Then someone explained that it was once called ORcharD Field, etc. I looked for the thread but couldn't find it. I mourn the loss of the "search all fora" function.

This is a similar question: where did the airline codes come from? Some, like United Airlines, make sense, but others like HP (America West) and WN (Southwest) don't. Are there explanations rooted in history or otherwise? Or are these just arbitrary combinations?

Mike