What the flight numbers on your boarding pass mean & why some will never be used
From the moment passengers arrive at the airport, flight numbers guide them through to the correct departure lounge and onto the flight they booked.
They also crucial for the likes of taxi companies for monitoring when their client will be landing.
However, there is more to the numbers than just a jumble of letters and digits.
In fact, there’s a lot of information hidden in your flight number, from the direction your plane is headed to how important that route is to the airline you’re flying with.
At the start of any of any flight number will be two or three letters, which most people know describes which airline you're flying with.
These codes are issued by the International Air Transport Association (IATA), the trade association for international airlines. And of course, no two airlines can have the same code.
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Many seem like no-brainers, for instance AA is American Airlines, BA is British Airways and NZ is Air New Zealand.
However, others are less obvious — like WN, which is the code for Southwest Airlines, and AY, which is used by Finnair.
When Southwest Airlines sought its code, SW was already taken — and is used to this day — by Air Namibia. That’s because Air Namibia used to be called South West Air Transport.
Similarly, Easyjet used to use the code U2 because EZ was already in use. But the budget airline now uses the three letter code EZY instead.
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Following the digits will be a set of numbers, which carry much more information about the flight.
Every single flight number has to be between one and four digits long, although there are certain numbers which will never appear.
The number 13 is never used due to superstition, while the number of the beast 666 is also one that is avoided at all costs.
Certain countries have different numbers that they won't use too.
For example, in China, the number four is considered unlucky because the word for four sounds a lot like the word for death, so that is used sparingly, if at all. Many hotels and buildings will also miss out the fourth floor for this reason.
However, the number eight is considered very lucky in China, so flight 888 would be a great plane to be flying on.
Meanwhile, American Airlines' flight AA1776 from Boston to Philadelphia pays tribute to the signing of the Declaration of Independence, which happened in Philadelphia in 1776.
The numbers also provide some information about the flight's possible destination.
For instance, north and eastbound flights will often be assigned an even number, while south and westbound flights will have odd numbers.
The return journey is often one number higher than the outbound flight too.
provided a great example of this, with JetBlue's flight from New York JFK to LA airport - the outgoing route is JBU523, while the returning leg is JBU524.
However, some airlines will do things differently, like Qantas. who use odd numbers for outbound international flights and even numbers for inbound international flights.
Certain flights are often seen as more important as others too, for which the airlines will typically assign lower numbers.
The rule is, that the lower the number, the more prestigious the route — such as Qantas’ Sydney-London service, QF1.
“Airlines often give lower numbers to their more prestigious, long-distance routes,” pilot Patrick Smith previously told news.com.au.
“If there’s a flight 001 in an airline’s timetables, it’s the stuff of London-Sydney or Paris-New York.”
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Meanwhile, these are what the codes mean on your boarding passes and which letters you never want to see.
And you can use your flight number to let your friends and family know where you are.
