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How Are Flight Numbers Determined?

Airport flight status

Are flight numbers chosen based on a rigid set of rules or are flight identification numbers a subjective decision made by individual airlines? The answer is a little bit of both.

In most cases, flight numbers appear as if chosen completely at random. Other identifiers, such as Fight 711 to Las Vegas, Flight 1776 to Philadelphia or Flight 1 from JFK to LAX, make it seem certain the airlines are choosing flight numbers for more creative reasons. If there is a method for decoding the hidden meanings behind flight identification numbers, it is a tough code to crack.

In practice, flight numbers are almost always determined by the airline’s individual rules and preferences — except when they aren’t.

The Basic Rules

According to The Foundation for Aircraft Selection, airlines are bound by only two hard and fast rules when choosing flight identification numbers. Airlines cannot reuse the same flight number for flights departing from the same airport on the same day and flight identification numbers can have a maximum of four digits.

A plane might fly under the same flight number for the entire day even if it is flown multiple routes, but another plane that makes a stop in a hub or visits the same airport twice or more might have multiple flight numbers throughout the day.

How Airlines Typically Determine the Numbers

While there aren’t many rules that govern how airlines select flight identifiers, carriers have traditionally used systems of their own device. Some airlines have historically used a flight numbering system similar to the way U.S. Interstate highways are numbered, with odd numbers assigned to flights headed south or west and even numbers for north- and east-bound planes.

In the past, airlines have used ascending flight numbers as planes depart throughout the day with lower numbers used for early morning flights and higher numbers reserved for the final trips of the day.

Airlines have also grouped flight numbers based on the region or country of origin. For example, all flights leaving from the West Coast might have flight numbers starting with 5 or all flights leaving South America starting with 23. Other carriers have used the exact opposite scheme, grouping flight number by region or country of destination. Airlines can even assign flight number ranges for all planes departing or arriving at a particular hub.

Despite the lack of stringent regulations, airlines are not completely free to pick and choose flight identifiers as they see fit. Some codeshare agreements require airlines to use a specific range of flight numbers. In the U.S., the Federal Aviation Administration will require airlines to change flight numbers if a similar number is already in use by another carrier in any given region.

Retired and Creative Numbers

Airlines with flights involved in the attacks of September 11 have vowed not to use those flight numbers ever again. Flight numbers for other infamous air disasters have also been retired by airlines. Likewise, flight numbers like 666 or unlucky 13 are avoided.

At other times, a number can be chosen for creative rather than practical reasons. Flight 1776 to PHL is indeed a nod to the signing of the Declaration of Independence in Philadelphia in 1776. Flight 1 is reserved for a given airline’s flagship route and lucky numbers are traditionally assigned to flights headed to gambling meccas and certain Southeast Asia destinations.

CNN reported that airline mergers have robbed much of the creativity from the art of assigning flight numbers. Fewer airlines flying more planes makes for a much more complicated system of assigning flight numbers with fewer numbers available to play with and long-held flight numbering traditions unique to the merged airlines are dropped in favor of uniformity.

The guidelines for setting flight numbers are constantly evolving. In 2011, the International Civil Aviation Organization (ICAO) considered a proposal to add the letter “D” to the identification number for delayed flights to avoid confusion or repeating the number of other scheduled flights later in the day.

[Photo: iStock]

Comments are Closed.
RUAMKZ May 27, 2015

Also other some specialty, city-specific numbers, much like the "1776" for PHL....... "1492" has been used by carriers to "CMH" and "711" for LAS. And since "8" is a lucky number in Chinese culture, numbers containing an "8" are often used by carriers going in and out of China. What drives me crazy, is when the flight numbers change on a daily basis....and this is due to the final destination of the plane. For example(though I cannot remember the exact number)is UA's SEA-EWR is one number, when it is a "stand-alone" flight....but a different number when it is SEA-EWR-CLE the following day.

jeffhacker May 26, 2015

Back in "the day," some airlines assigned flight numbers based on equipment type. For example, Delta's DC8 flights were all 8XX; Their Convair 800's were all 9XX, etc. with a similar convention for other types. Some airlines assigned flight numbers based on routes (i.e., U.S. South-American routes on Braniff were 9XX, a convention that continued when Eastern took over the routes, and now with American which continues the tradition).

98103 May 26, 2015

And they come up with creative "same flight number change of plane" service which is confusing to passengers who don't fly very often. They think they're getting a one stop through flight from X to Y, but really, it requires a change of planes (often aircraft types -- from a 737 to a 767 for example). It's no better than a scheduled change of aircraft, but it is done expressly to show the airline offers direct service, when in reality, none exists.


Other way. LHR to JFK was 001. 002 was JFK to LHR. BA1 is LCY to SNN to JFK now, while BA2 is JFK to LCY on the babybus.

Centurion May 24, 2015

British Airways Concorde Flight 001 was JFK to LHR. Certainly not random