What Are Flight Numbers, and Why Are They Important?

PUBLISHED ON 02.21.2022

Most travelers recognize the importance of flight numbers as a tool for finding their gate or picking someone up from the airport on time. Besides that, you probably don’t pay much attention to them.

Flight numbers aren’t simply arbitrary numerals that help you reach your destination. They’re part of a code that helps airlines and air traffic control track airborne flights.

Cracking the Code: Breaking Down Flight Numbers

A flight number is an alpha-numeric protocol for identifying specific airline routes. The official term, as defined in the Standard Schedules Information Manual, or SSIM, is flight code or flight designator.

The International Air Transport Association, a trade organization that helps to regulate and support the airline industry, issues the letter-based code that represents the airline, which usually consists of two or three letters. These specify the airline.

The numbers that follow differentiate the routes. But assigning a flight code isn’t done in the same way as allocating a phone number. The numbers can represent different types of flights.

Most flights have a fixed route that goes between points A and B. Your flight number usually changes during a layover, however. That’s because you’re likely switching to a different carrier or different route. Although some flight codes are used for routes with three legs, not all of the passengers will continue to the third destination. If your next flight is with a different carrier, the airline code will change as well.

Air traffic control uses flight numbers to keep track of the paths of aircraft. Unique identifiers for the flight provide a way to organize, regulate and monitor air traffic flow.

Flight Number Conventions and Standards

Many airlines follow the same standards. However, there is some variation among carriers.

For example, many airlines use even numbers to indicate northbound and eastbound flights. Odd numbers are reserved for southbound and westbound flights. However, an airline may assign an odd number to an outbound flight and the next consecutive even number to its corresponding inbound flight.

Lower flight numbers are typically given to prominent routes. Long, popular and high-revenue routes often have low flight numbers, such as Delta’s DL1 flight, which provides service between New York’s JFK and London’s Heathrow airport, which was Delta’s first international destination. Because these flight numbers are low, they usually have fewer than three digits, although some are in a multi-digit format that starts with 0, such as 01 or 001.

Regional affiliate flights are often designated with a four-digit number between 3000 and 5999. Flight numbers greater than 6000 are typically codeshare flights. These are operated by partner airlines, which sell seats for the operating carrier to allow passengers to visit multiple destinations on a single itinerary.

When your boarding pass reads, “Operated by British Airways” beneath the American Airlines flight code, this indicates that it’s a codeshare flight. British Airways is the operating carrier—the company flying the plane. American Airlines is the marketing carrier.

Sometimes, an empty aircraft must be moved to a different location. These ferry flights, or empty leg flights, are identified with numbers between 8000 and 9000.

How Does Your Favorite Airline Use Flight Numbers?

American Airlines uses the same numbers for inbound and outbound flights on the same route. This may be confusing for some travelers because it requires them to make sure that they’re looking at the correct departure and arrival airports when they’re trying to identify the flight. However, it makes sense from an air traffic control standpoint because both flights can’t be airborne simultaneously.

When Southwest Airlines launched, the airline code SW was already taken by Air Namibia, which was originally called South West Air Transport. Southwest Airlines adopted the identifier WN. There are many theories about what WN stands for. Some say that one of Southwest’s executives was a Willie Nelson fan. Others wonder whether WN stands for “Why not” or “We’re nuts.”

United Airlines gives a nod to the Indy 500 with flight UA500, which flies between Indianapolis and San Francisco. Alaska Airlines identifies its Seattle-Pittsburgh flight with 412, Pittsburgh’s area code. Jet Blue, Spirit Airlines and Frontier Airlines run lucky flights with number 777, which land in Las Vegas.

What Flight Numbers Do Airlines Avoid?

Airlines avoid assigning certain numbers to any flights. For example, 757 and 737 are rarely used because they could be confused with the aircraft models. Superstition leads airlines to avoid 13 or 666.

However, in October 2017, Finnair sent flight number 666 to HEL on Friday the 13th. The flight was real, but the naming convention was done as a joke for over a decade. The flight traveled from Copenhagen, or CPH, to Helsinki, or HEL.

If a particular flight number is associated with a prominent, negative event, the airline might retire it. After the attacks on September 11, 2001, American Airlines stopped using flight code AA11 for its Boston-Los Angeles route. Malaysia Airlines flight MH370, which disappeared during a flight in 2014, was also retired.

How Are Charter Flights Numbered?

Charter flights use the same numbers as ferry flights. They’re typically a four-digit number that begins with eight. This convention is not always followed, but private flight numbers are uncommon so that they can be easily distinguished from commercial flights.

Don’t Confuse These Aviation Codes

If you’re flying commercially, you’ll see a few different numbers and codes on your boarding pass. Don’t confuse flight codes with the other codes, which include:

  • Airline code – The first two letters of the flight number represent the IATA airline code. The International Civil Aviation Organization, or ICAO, uses a different standard, which may be reflected on some documents. American Airlines’ IATA code is AA but its ICAO code was changed to AAL in 1988.
  • Airport code – Similar to an airline code, the airport code is usually a three-letter representation of each airport.
  • Confirmation code – Also known as a record locator, this number helps ticketing agents pull up your itinerary.

There are differences between flying first class and traveling via private jet charter. If you’re flying on a private charter jet, you won’t use a boarding pass. You’ll leave out of a Fixed Base Operator, or FBO, bypassing the need to go into the regular airport terminal or deal with TSA security. Here are four FBOs in Teterboro, NJ, for example.

You’ll locate a private charter flight by its tail number. This consists of a letter that represents the country in which the aircraft is registered and up to five alphanumeric digits. It’s like a license plate number on a car. Every aircraft in a fleet of private jets has a different tail number. You can use the tail number to track a private charter jet’s flight path in real time.

Commercial airlines also have tail numbers on their aircraft. However, passengers typically don’t have to refer to the tail number for anything. Commercial flights are identified by flight number.

There are so many benefits of flying private instead of commercial. Skirt the crowds and travel with comfort and confidence when you book a private charter flight with us. You’ll save valuable time when you don’t have to deal with TSA security, boarding passes and flight numbers. The only documentation that you need to fly a private charter jet is valid identification.

Private air charter companies put safety and security first. Know who you’re traveling with. Private charter flights are perfect for those who require discretion.

Don’t waste time. Contact us to book your on-demand private charter flight today. Travel on your schedule, and take charge of your itinerary. Plus, you’ll fly in comfort, with every convenience provided until you have reached your destination.


Jordan Brown


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