Look at your luggage tag or air waybill and you'll see airport codes instead of origin and destination city names spelled out. IATA (International Air Transport Association) assigns a three-letter identifier code to every commercial airport in the world. (By the way, pronounce it "Eye-ah-ta,") It's no mystery how IATA came up with BOS for Boston or STL for St. Louis. But why the heck did it assign MCI to Kansas City, IAD to Washington Dulles or EWR to Newark?

Turns out there was method to the madness. When they started assigning IATA codes, certain prefixes were set aside. The Navy grabbed the "N" prefixes. Navy pilots train at NPA (Navy Pensacola), for instance. Take away the "N" from Newark and EWR makes sense. Nacogdoches, TX? OCH.

With few exceptions, prefixes beginning with "W" or "K" are generally not used for USA airports lest they be confused with radio station call letters. So before Washington Dulles opened they were leaning toward DIA (Dulles International Airport) but then realized that it might be too easily confused with nearby Reagan (DCA—District of Columbia Airport), especially when harried freight clerks were scribbling chalk letters on baggage carts. Stick the D at the end and International Airport Dulles doesn't seem so crazy.

Long before the Wright Brothers, the National Weather Service dotted stations around the country with two letter city codes. Later, IATA adopted some of those by simply adding an X. That's why we might ship from Portland, OR (PDX) to Los Angeles (LAX).

JFK Airport is a rarity in that it changed IATA code from IDL when it changed its name from Idlewild. Usually once a code is assigned, it stays assigned. So if you hop on board a flight to Indianola, MS and have a really old pilot, you might want to make sure he doesn't head for New York seeing how Indianola took over Idlewild's discarded IDL.

An IATA code that starts with Y probably means your freight is probably headed for Canada. Literally hundreds of Canadian airport codes begin with Y.

Who wants to be FAT? Fresno Air Terminal doesn't mind. How do they get CMH out of Columbus? From Columbus Municipal Hangar. Puzzled on CVG being Cincinnati? Cincinnati's airport actually sits across the Ohio River in Covington, KY.

File MCI for Kansas City under "too late now." Because of the initial letter K restrictions, the original Kansas City airport was MKC (Missouri Kansas City). When they started planning a big new airport someone decided that Mid-Continent International sounded pretty darned fancy and got the MCI designation. Before the airport opened, local politicians decided to change the name to Kansas City International so that travelers would recognize their fair city. Meantime, it was too late to change the MCI code.

Okay, I've kept you in suspense long enough. You're wondering about ORD for Chicago O'Hare, aren't you? Midway (MDW), its cross town rival, was bursting at the seams as the world's busiest airport in the early days of commercial jets. Officials decided to build a huge new airport northwest of town where a tiny airstrip that had been renamed for heroic Navy pilot, Lt. Cmdr. Butch O'Hare. As MCI will vouch, once you get an IATA code it's almost impossible to change it.

What was the name of the little strip before they changed it to O'Hare? Orchard Field—ORD.