Every year, millions of tourists pass through airports across the world. Whether you’re travelling to a new destination, heading home to see family or off on a business trip you’ve likely gone through an airport with a mysterious X in its name.

For example, Los Angeles Airport is known as LAX or Birmingham as BHX. A recent thread on social media site Reddit questioned what this ‘X’ means, gardening thousands of comments of people wondering if it means ‘express’ or ‘international’ – however the truth is much stranger. According to Airport Luxury Transfer experts, SCS Chauffeur, the truth is that the “X” has no secret aviation meaning at all.

Hadleigh Diamond, Luxury Airport Transfer provider, said: “It’s a leftover from the 1930s and 1940s, when the aviation industry expanded airport codes from two to three letters to improve communication across telex and radio systems.

“Los Angeles was originally assigned “LA”, and Birmingham “BH”—but when the global coding system required three letters, both airports simply added an “X” to fill the gap.

“It’s not an abbreviation or a secret symbol, just a historical quirk from the early days of international aviation.”

Airport codes are everywhere from baggage tags to boarding passes and now that you understand what the X means it can help to decode travel abbreviations.

Make sure you don’t get confused between BHX for Birmingham in the UK and BHM for Birmingham in Alabama.

Hadleigh said: “Travellers often assume the ‘X’ stands for something technical, but it’s really a relic from a much simpler time.

“LAX and BHX are perfect examples of how aviation history quietly lives on in the details we see every day – even on our boarding passes.

“Knowing where these codes come from is a fun reminder of how fast air travel evolved.”