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Why do commercial airflights have those letters and numbers? Here’s why!

Published on November 23, 2025

Image: Erik Odiin

Airport codes, numbers, and technical lingo might seem arcane or even random at first glance, but most have surprisingly logical origins. From international abbreviations to behind-the-scenes terms used by airport staff, there’s a whole coded world buzzing around your flight. Let’s unpack 10 of the most widely used ones.

IATA airport codes

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IATA airport codes are those three-letter codes you see on tickets and baggage tags, like LAX for Los Angeles or JFK for New York. They're set by the International Air Transport Association (the aforementioned IATA).

These codes often reflect the airport’s name or location, but not always. Some are not as obvious, like ORD for Chicago O’Hare, which comes from its previous name: Orchard Field.

UN/LOCODEs (Trade and Transport Locations)

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A relative of the IATA airport codes, UN/LOCODEs are five-character codes used in global trade and transport. They combine a two-letter country code with a three-letter location code, like USLAX for Los Angeles in the U.S.

These codes help standardize locations in shipping, logistics, and customs. You might not see them as often as airport codes, but they’re essential behind the scenes in moving goods worldwide.

Airport Terminal and Gate codes

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Airport terminal and gate codes help guide you through the airport. A sign like T1-G12 means Terminal 1, Gate 12.

Each airport has its own layout, so the letters and numbers can vary. Some use concourses (like B42), while others just number gates.

Runway designators

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Runway designators are those numbers you see at each end of an airport runway, like 09/27. They’re based on compass directions. For example, 09 means 90°, or east, and 27 means 270°, or west.

If there are parallel runways, you’ll see letters too, like L for left or R for right (e.g., 09L/27R).

Airline and flight number codes

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Airline and flight number codes help identify specific flights, like AA100 for American Airlines Flight 100. The first part is the airline’s IATA code, followed by a number assigned to the route.

These codes are used in schedules, boarding passes, and announcements.

A-CDM codes (Airport Collaborative Decision Making)

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A-CDM codes are used at airports to help controllers and pilots work together smoothly using universal directives. They stand for Airport Collaborative Decision Making.

Some examples of these kinds of codes are TOBT (Target Off-Block Time) and TSAT (Target Start-up Approval Time), which help coordinate when planes should push back or start engines.

METAR/TAF airport codes (for weather reports)

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METAR and TAF codes use ICAO airport codes to report weather conditions for pilots and flight crews. For example, EGLL is used in METAR reports for London Heathrow.

These reports include info like wind, visibility, and temperature. METARs show current weather, while TAFs give forecasts.

Baggage tag codes

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Baggage tag numbers and codes are the barcodes that are attached to the luggage when it is checked. They usually include the airport's IATA code, like LAX123456, to help route the bag correctly.

These tags let airports and airlines track bags from drop-off to arrival.

Flight status

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Flight status codes are seen on airport screens, like ON TIME, DELAYED, or BOARDING, to keep passengers updated. They’re simple but super helpful when you’re rushing to your gate.

Other codes can be spotted, like DEP (Departed), ARR (Arrived), ETA (Estimated Time of Arrival), and GATE CLOSED.

Flight number

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Flight numbers help identify each flight and usually include four or five digits after the airline code. These numbers aren’t random: they often reveal details like the route, destination, or flight type.

For example, Lufthansa uses 400s for North America and 900s for Asia. Some airlines even assign numbers based on the country of origin.

Embark on a vocabulary journey

Nightmare, curfew, brunch and more! Curious origins of 10 everyday words

Published on November 23, 2025

Image: Snapwire

Thanks to etymology, the science that studies the origins of words, we can learn how and when certain terms began to be used and why they are popular today. Did you know that the concept of brunch has existed since the 19th century? And that we owe the word clue to the myth of Theseus and the Minotaur? Would you like to discover these and other curious origins of common words we use on a daily basis? Keep reading!

Nightmare

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The night part in "nightmare" is self-explanatory, but what about "mare"? You may be interested to know that a mare is not only a female horse but also a term that comes from Middle English and means "suffocating evil spirit." Back in the 13th century, a mare was thought to be a female goblin or ogre that lay on sleeping people and suffocated them.

People were so convinced that a physical being caused this distress that a nightmare was believed to be an actual monster until the 16th century. Eventually, people realized that the crushing, suffocating feeling was an emotional reaction to a bad dream. Isn't that what a nightmare feels like—panic, shortness of breath, suffocation? Fortunately, we have a perfect word to describe it!

Curfew

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Didn't you hate it when you were young and your parents set a curfew for you? Surely you didn’t know that this custom comes from the sounding of a bell reminding medieval Europeans to cover their fires at night. Today, a curfew is imposed by parents on rebellious teenagers or during periods of emergency or conflict as a way of keeping people off the streets at night.

However, in the Middle Ages, the curfew was the time when people were reminded not to set their own homes on fire. Back then, an evening signal bell would give the order "Cover fire!" But what exactly does curfew mean? Well, the term curfew is an Old French word brought to England by the Norman conquerors, which comes from cuvrir, "to cover" and feu, "fire."

Scavenger

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A long, long time ago, before there were machines, a scavenger was a person who swept the streets. Their job was to remove trash and dirt from the roads. Some of them may have pocketed items they found while pushing around their brooms, but that’s not what gave rise to the modern concept of a scavenger.

For that, the English language has tax collectors to thank. In London, those tasked by the crown with collecting a form of tax called scavage from foreign merchants were called scavagers. By the 16th century, the word was modified by adding an "n," mutating it to scavengers, used to describe people who combed through looking for useful items. Later, the concept was borrowed for animals such as vultures and hyenas.

Silly

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If someone called you silly today, you would be offended, but a medieval Englishman would have been pleased. The word is an alteration of the earlier term seely, from an Old High German root meaning "luck, happiness." Therefore, the Old English sense of seely was "happy, fortunate, blessed by God."

In the later Middle Ages, the term developed into "holy," then "innocent, defenseless, deserving of pity." So, what happened? How did we go from a positive term to one with a more negative connotation? The simple explanation is that people often regard goodness and simplicity as a lack of intelligence, which is why, since the late 16th century, the primary sense of silly has been "foolish."

Vaccine

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We all know that vaccines save lives, but few know where the term comes from. Believe it or not, its origin is in the animal world. In the 18th century, English physician Edward Jenner observed that milkmaids who had come into contact with the virus causing cowpox did not contract smallpox, a more serious disease. In 1796, he deliberately infected a couple of children with small amounts of cowpox and proved his theory.

Two years later, Jenner reported his findings in an article written in Latin in which he referred to cowpox as variolae vaccinae, derived from vaccus, meaning "cow." Thus, at the dawn of the 19th century, the term vaccine, used at the time to refer to cowpox material used for injections, later evolved into other nouns and verbs such as vaccinate and vaccination.

Amateur

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Today, for some reason, the word amateur has a negative connotation. However, in its origins, it had a much more positive meaning. Borrowed from French in the 18th century and ultimately derived from the Latin word amator, meaning "lover," it was originally used to describe a person who loves or is fond of something, as well as a person who practices an art or sport as a hobby rather than professionally. In other words, an amateur does something for love rather than for money.

Interestingly, the word aficionado, a synonym for "amateur," started out as a term for an aspiring bullfighter and later came to refer to a devotee of bullfighting. Aficionado is a Spanish word meaning "to inspire affection" and is now used to describe any ardent follower of an activity.

Sarcasm

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The words of a sarcastic person can be sharp and painful, and this may be because the term sarcasm hides the idea of biting into the flesh. The word came into English in the mid-16th century from French, and is based on Greek sarkazein, meaning "to tear flesh," which also came to mean "to gnash the teeth" or "speak bitterly."

Interestingly, the word sarcophagus has a similar history. The original Greek term meant "flesh-eating" and is a combination of sarx, meaning "flesh," and -phagos, meaning "eating." Sarcophagi were originally made of a type of limestone that the ancient Greeks believed consumed the flesh of any dead body in contact with it.

Clue

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Without clues, Sherlock Holmes and Hercule Poirot would not be the detectives we know and love. The word clue is a modern spelling of the Old English term clew, meaning "a ball of thread." How did we go from a thread to our modern sense of clue? Well, it derives, no less, from the myth of Theseus and the Minotaur.

After killing the bull-headed monster, the Greek hero manages to escape the labyrinth thanks to the ball of twine that Princess Ariadne gave him to find his way out. From this ancient story, a clue became anything that you can follow to reach a solution.

Brunch

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Brunch conjures an image of a contemporary urban lifestyle. Although we all picture a cool New Yorker coining the term in the 20th century, it actually came into being in 19th-century Britain. Back then, many upper-class families would give their servants Sundays off, during which the servants would prepare a buffet that included breakfast and lunch dishes. Hence, brunch is a combination of the words breakfast and lunch.

Don’t believe us? An 1896 article in the "Fashionable and Seasonable" section of the English satirical magazine Punch stated: "Nowadays to be fashionable, we have to go ‘brunching.’ An excellent compound word, introduced, by the way, last year by Mr. Guy Beringer in the now-defunct Hunter's Weekly magazine, indicating a combination of breakfast and lunch." Later, in the 1930s, the practice became popular in the United States.

Caterpillar

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If you own a garden, you’ve probably seen a caterpillar or two eating away at the leaves of your precious plants. If not, you might remember the blue smoking character from Alice in Wonderland. But do you know where the peculiar name of this furry insect comes from?

The term caterpillar first appeared in English in the form catyrpel, probably an alteration of the Old French word chatepelose, which literally means "hairy cat." The extended form -piller is believed to come from the Old English word piller, meaning "a plunderer or ravager." Given the damage that caterpillars do to plants, it is likely that this influenced how the word is now spelled.