Travel & Day Trips

San Francisco Airport’s Code: Where Did It Come From?

Every airport in the world has a unique three-letter code, issued by the International Air Transport Association (IATA). These codes are used in flight planning, ticketing, baggage handling, and more.

But have you ever wondered where these codes come from, or why San Francisco International Airport’s code is SFO?

Let’s delve into the story behind it.

A Bit of History

The IATA, which assigns these codes, is a trade association of the world’s airlines. Founded in 1945, it represents about 290 airlines from 120 countries, covering 82% of total air traffic.

In the early days of aviation, airports used two-letter codes based on the weather stations at the airports. As air travel grew, a need arose for more combinations, and the system expanded to three letters.

Decoding SFO

The code for San Francisco International Airport is SFO. But why is that the case? As the SFO Museum recently shared, the answer lies in the airport’s history.

Table 1. Decoding SFO


The ‘S’ and ‘F’ come from the first letters of San Francisco. As the museum shares, “Some of the two-letter codes that existed before that simply had an ‘X’ added for international airports, such as LAX and PHX. SF was given an ‘O’, however, that worked nicely for the ‘o’ in Francisco, and thus became SFO.”

The use of ‘O’ to represent ‘Airport’ is a common practice in airport naming conventions, especially for airports that have switched from a two-letter to a three-letter code. For instance, Moscow Sheremetyevo is SVO.

Other U.S. Airport Code Oddities

SFO isn’t the only airport with an interesting code. Here are a few others:

  • Los Angeles International Airport (LAX): The ‘X’ was appended when airports switched from two-letter to three-letter codes, and stood for “International”
  • Louis Armstrong New Orleans International Airport (MSY): The code comes from the airport’s original name, Moisant Stock Yards.
  • Chicago O’Hare International Airport (ORD): The code comes from the old Orchard Field, on which the airport was built.
  • Orlando International Airport (MCO): The code comes from the airport’s former name, McCoy Air Force Base.
  • Maui Airport (OGG): This airport was named for Jim Hogg, a famous Hawaiian Airlines pilot.


Airport codes, while seemingly random letters, often have intriguing stories tied to the history and geography of their locations. The next time you’re waiting for a flight at SFO or any other airport, take a moment to appreciate the small piece of aviation history in your ticket.

Thomas Smith

Thomas Smith is a food and travel photographer and writer based in the San Francisco Bay Area. His photographic work routinely appears in publications including Food and Wine, Conde Nast Traveler, and the New York Times and his writing appears in IEEE Spectrum, SFGate, the Bold Italic and more. Smith holds a degree in Cognitive Science (Neuroscience) and Anthropology from the Johns Hopkins University.

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