I was reading an old aviation magazine at my dentist’s office — don’t ask why they had it — and stumbled on a photo of a 1930s weather station with a two-letter code painted on its roof. That kicked off a rabbit hole I’m still not fully out of. Turns out, airport codes have about a century of history behind them, and almost none of it went according to plan.
It All Started with Weather Stations
Before airports even had codes, the National Weather Service was using two-letter identifiers for weather reporting stations scattered across the country. Pilots in the early days of commercial aviation borrowed those same labels because, well, they were already there. Why reinvent the wheel?
The problem was that two letters only gives you 676 combinations. As more airports opened through the 1930s, the system started running out of room fast. Something had to give.
Adding That Third Letter — And the X Mystery
Probably should have led with this, because it answers a question almost every traveler has asked: why does Los Angeles end in X? LAX. Portland — PDX. What’s with the X?
When the industry switched to three-letter codes in the late 1930s and 1940s, airports that already had two-letter weather station codes just tacked an X on the end as a placeholder. LA became LAX. PD became PDX. That X doesn’t stand for anything. It’s literally filler. I love that — one of the most recognized airport codes in the world exists because someone needed a third letter and just went “eh, X works.”
ICAO Brought Some Order to the Chaos
By 1947, the International Civil Aviation Organization decided the whole thing needed more structure. They introduced four-letter codes with built-in geographic logic. The first letter tells you the region — K for the continental US, C for Canada, E for Northern Europe. So London Heathrow isn’t just LHR to a pilot; it’s EGLL. That E tells you Northern Europe, the G narrows it to the UK.
I’ll be honest, I find the ICAO system more satisfying than the IATA one. It actually makes sense structurally. But it never caught on with the public because nobody wants to type four letters into a booking engine when three will do.
How New Codes Get Assigned Today
These days, getting a new airport code is a formal process. You apply to IATA, tell them what you want, and they check if it’s available. Preference goes to codes that match the city or airport name, but the good ones are mostly taken. When airports close down, their codes sometimes get recycled — though IATA usually sits on recently-used codes for a while so nobody books a flight to an airport that doesn’t exist anymore.
That’s what makes the whole history endearing, honestly. It started as weather shorthand, grew into a patched-together system held together by habit and inertia, and somehow became the universal language of air travel. A hundred years of improvisation, and it still works. Mostly.
