ICAO vs IATA Codes

ICAO versus IATA codes has gotten complicated with all the conflicting explanations flying around. I spent an embarrassing amount of time early on mixing up the two systems, and I know I’m not alone in that. So let me break this down the way I wish someone had explained it to me years ago.

The Quick Version

Probably should have led with this: IATA codes are three letters — the ones on your boarding pass. ICAO codes are four letters — the ones pilots file flight plans with. For US airports, ICAO adds a K prefix to the IATA code. So Los Angeles is LAX to travelers and KLAX to pilots. London Heathrow is LHR on your ticket and EGLL on a pilot’s chart. Different organizations, different purposes, same airport.

That’s what makes the dual system endearing in a nerdy sort of way. Two entire global organizations looked at the same set of airports and came up with completely separate naming conventions, and somehow the whole thing works. Learn the codes for your region first, branch out from there, and use reference sources like AirNav or SkyVector when you need to cross-check. It clicks faster than you’d expect.