Flight Number Assignments

How Are Flight Numbers Determined?

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]

flight 1flight 1776flight numbersicaointernational civil aviation organization

A flight number, when combined with the name of the airline and the date, identifies a particular flight. This callsign should not be confused with the tail number of the aircraft, although both can be used as a call-sign as used in general aviation. A particular aircraft may fly several different flights in one day, and different aircraft may be used for the same flight number on successive days.


A number of conventions have been developed for defining flight numbers, although these vary widely from airline to airline. Eastbound and northbound flights are traditionally assigned even numbers, while westbound and southbound flights have odd numbers. Other airlines will use an odd number for an outbound flight and use the next even number for the reverse inbound flight. For destinations served by multiple flights per day, numbers tend to increase during the day. Hence, a flight from point A to point B might be flight 101 and the return flight from B to A would be 102, while the next pair of flights on the same route would usually be assigned codes 103 and 104.

Number of digits[edit]

Flight numbers of less than three digits are often assigned to long-haul or otherwise premium flights. Flight number 1 is often used for an airline's "flagship" service. For example, British Airways flight 1 was the early morning supersonicConcorde service from London to New York City and is now a premium business-class only flight between the same cities; Air New Zealand flight 1 is the daily service from London to Auckland via Los Angeles; Qantas flight 1 is the daily Kangaroo Route from Sydney via Dubai to London. American Airlines Flight 1 is the daily flight from New York to Los Angeles; United Airlines Flight 1 is the daily flight from San Francisco to Singapore; and El Al flight 1 is the daily overnight service from Tel Aviv to New York City. Four-digit numbers in the range 3000 to 5999 typically represent regional affiliate flights, while numbers larger than 6000 are generally codeshare numbers for flights operated by different airlines or even railways.

Likewise, flight numbers larger than 9000 are usually referred to as ferry flights, that carry no passengers and are used to designate aircraft being repositioned to or from a maintenance base or from one air travel market to another, where it is supposed to start a new commercial flight. Flight numbers starting with 8 are often used for charter flights, but it always depends on the commercial carrier's choice.

List of flight number 1 by airlines[edit]

Most flights are non-stop from A to B, and few are from A to B then to C (both A-B and B-C have flight number 1). Aircraft type may change due to operation need.

Note*: BA1 stop at Shannon, Ireland only for refueling and all on-board passengers go through the U.S. Immigration and Customer at the meantime.

Flight number changes[edit]

Flight numbers are often taken out of use after a crash or a serious incident. For example, following the crash of Alaska Airlines Flight 261, the airline changed the flight number for subsequent flights following the same route to 229. Also, American Airlines Flight 77, which regularly flew from Dulles International Airport in Washington, DC, to Los Angeles International Airport, was changed to Flight 149 after the September 11, 2001 attacks. On the other hand, other considerations may lead an airline not to change a flight number; for instance, the aforementioned "flagship" American Airlines Flight 1 retains its designation despite a major accident in 1962. There are at least three instances of flight numbers that have suffered two serious accidents: Flight 253 of Linea Aeropostal Venezolana (both in 1956, the first in June, and the second in November), Flight 869 of United Arab Airlines (the first in 1962 and the second in 1963), and Flight 800 of TWA (the first in 1964 and the second in 1996). Another example of this is the retirement of MH370 and MH371 Of Malaysian Airlines after an aircraft disappeared in 2014.

Flight number conservation[edit]

Airline mega mergers, in markets such as the United States, have deemed it necessary to break conventional flight numbering schemes. Organizations such as IATA, ICAO, ARC, as well as CRS systems and the FAA's ATC systems limit flight numbers to four digits (0001 through 9999). The pool of available flight numbers has been outstripped by demand for them by emergent mega-carriers. As such, some carriers have resorted to using the same flight number for back-and-forth flights (e.g. DCA-PBI-DCA), or in other cases carriers have resorted to assigning a single flight number to an eight-leg flight (e.g. ICT-DAL-HOU-MDW-OMA-DEN-ABQ-LAS-BDL).[33]

Flight designator[edit]

Note that, although 'flight number' is the term used colloquially, the official term as defined in the Standard Schedules Information Manual (SSIM) published annually by the International Air Transport Association (IATA) Schedules Information Standards Committee (SISC), is flight designator. Officially the term 'flight number' refers to the numeric part (up to four digits) of a flight code. For example, in the flight codes BA2490 and BA2491A, "2490" and "2491" are flight numbers. Even within the airline and airport industry, it is common to use the colloquial term rather than the official term.


Flight numbers are also sometimes used for spacecraft, though a flight number for an expendable rocket (say, Ariane 5 Flight 501) might more reasonably be called the serial number of the vehicle used, since an expendable rocket can only be launched once. Space Shuttle missions used numbers with the STS prefix, for example, STS-93.

See also[edit]


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