Annex 7 – Aircraft Nationality and Registration Marks


Annex 7

Developed by ICAO, the International Standards and Recommended Practices (SARPS) contained in the nineteen Technical Annexes to the Convention on International Civil Aviation (also called Chicago Convention) are applied universally and produce a high degree of technical uniformity which has enabled international civil aviation to develop in a safe, orderly and efficient manner.


Annex 7 Aircraft Nationality and Registration Marks adopted by the International Civil Aviation Organization (ICAO) provides Standards & Recommended Practices for the display of appropriate aircraft nationality marks, common marks and registration marks which have been determined to comply with Articles 17 to 21 of the Chicago Convention.

The concept of nationality for aircraft was adapted from maritime law where the national flag is used to indicate a ship’s country of registration. The questions related to technical and legal aspects relevant for the future of aviation, among which was that of aircraft registration, were considered at the Paris Conference of 1910. While this Conference was unsuccessful in that it did not result in a signed agreement, the draft it produced subsequently formed the basis for the 1919 Paris Conference. The First Commission of the latter Conference, that dealt, among other things, with the registration of aircraft, came up in Annex A - Registration of Aircraft with a list of nationality marks for the participating countries; it is to be noted that the identification with one letter for five countries was based on the call sign prefixes adopted by the 1912 Radiotelegraph Conference, held in London. The intention being that other states adopting later the Convention Relating to the Regulation of Aerial Navigation should inform the International Commission for Air Navigation (ICAN) of the nationality mark chosen. The Commission would act as the coordinating body, ensuring that they did not duplicate those already allocated.

Final Protocol related to the International Radiotelegraph Convention signed in London in 1912.

At the second Session of ICAN held in London in October 1922, the French Delegation suggested that it would be more practical to adopt the same letters for aircraft nationality marks as those allocated for use as wireless call signs. For reference, at the London International Radiotelegraph Conference, held in London from 4 June to 5 July 1912, the International Telegraph Union (ITU, known as from 1 January 1934 as the International Telecommunication Union) had already made a list of letters to be used as call signs for wireless calls; the resulting International Radiotelegraph Convention came into force on 1 July 1913. Although initial allocations of the latter Convention were not specifically for aircraft but for any radio user, the Convention Relating to the Regulation of Aerial Navigation thus made allocations specifically for aircraft registrations based on the 1913 call sign list and its further revisions adopted at the ITU Conferences: the International Radiotelegraph Conference held in Washington, USA from 4 October to 25 November 1927, the International Radiotelegraph Conference held in Madrid, Spain from 3 September to 10 December 1932, the International Radio-communications Conference held in Cairo, Egypt from 1 February to 8 April to 1938).


According to the latest version of the Convention Relating to the Regulation of Aerial Navigation, the nationality and registration marks borne by the aircraft shall be constituted by a group of five letters:

1.         The nationality shall be indicated by the first letter or the first two letters of such group, selected from the series of nationality symbols included in the radio call signs allocated to the state of registry by ITU.

2.        A hyphen shall be placed immediately after the nationality letter or letters.

3.        The registration shall be composed of three or four letters, forming with the nationality a maximum of five letters. Examples: F-ABCD or HS-XYZ.

4.        The nationality and registration marks shall be painted on the aircraft or affixed by any other means ensuring a similar degree of permanence.

5.        The letters shall be capital letters in Roman characters without ornamentation.


List of country prefixes for the 27 States which signed the Convention Relating to the Regulation of Aerial Navigation on 13 October 1919.

The aircraft marks identify distinctively a civil aircraft, in similar fashion to a license plate on an automobile. The markings have been amended and completed over the years. With the coming into existence of the permanent International Civil Aviation Organization (ICAO) in April 1947, the status of the standards prepared at the Chicago Conference underwent major changes. So, the original Annex H - Aircraft Registration and Identification Marks became Annex 7 - Aircraft Nationality and Registration Marks. The ICAO Council adopted the first standards concerning this issue on 7 February 1949; they became effective on 1 July 1949. The standards on markings have been amended by ICAO over the years.

Annex 7 to the Chicago Convention prescribes the size, format and position the nationality and registration marks on the hull of the aircraft, and also the format of the Certificate of Registration that is to be carried in the aircraft at all times. The nationality mark (prefix) should precede the registration mark (suffix). Depending on the country, the registration mark is a numeric or alphanumeric code and consists of one to five digits or characters. In accordance with Para 2.3 of Annex 7, the nationality marks shall be selected from the series of nationality symbols included in the radio call signs allocated to the State of Registry by the International Telecommunication Union (ITU) (making the registration a quick way of determining the country of origin) and shall be notified to ICAO. The letters shall be capital letters in Roman characters without ornamentation; the numbers shall be Arabic numbers without ornamentation.

Isle of Man (United Kingdom) – 1984 - 40th Anniversary of ICAO and 50th Anniversary of the first official airmail service to the Isle of Man. Maximum Card.

 Britten-Norman BN-2A-26 Islander of Haywards Aviation

(Registered G‑AXXJ in United Kingdom, c/n 150, 1970).

A hyphen or dash separates the nationality mark and the registration mark, except in the United States of America where the nationality mark is N immediately followed by a set of alphanumeric characters for the registration; the registration number is also referred to as an "N-number", as all aircraft registered in the USA have a number starting with N (example: N26789 used for Grumman American Avn. Corp, Serial number AA5A0723, Model AA-5A).

The Supplement to ICAO Annex 7 provides information with regards to differences between the national regulations and practices of Contracting States and the corresponding international standards contained in Annex 7; it also provides the list of aircraft nationality marks, national emblems and common marks.


At the time when the Chicago Convention was adopted, commercial aircraft were predominantly purchased directly by their operators who then retained ownership of such aircraft for use during most or all of their useful lives. Changes to aircraft nationality were not common since an aircraft tended to reside within one State for most or all of its useful life. However, over the past three decades, aircraft operators have realized substantial capital and operational efficiencies by leasing (rather than owning) a portion of their fleets for various periods of time. Based on various studies, the aircraft leasing market will continue to grow.


As a result, aircraft will most likely be transferred from one operator to another changing nationality multiple times during their useful lives. The change of aircraft nationality or registration from one State to another is referred to as cross-border transfers of aircraft. The increase in the number of cross-border transfers of aircraft globally, along with differences in States’ regulations, requirements and practices has highlighted certain inefficiencies in a global system that was developed when cross-border transferability was relatively uncommon.


In 2017, ICAO launched the cross-border transferability initiative with the aim of improving, standardizing and enhancing the efficiency of the cross-border transfers of aircraft and at the same time, ensuring that aviation keeps and improves its remarkable safety record. With the support of subject matter experts from Member States, international organization and industry, ICAO is currently undertaking a structured review of relevant ICAO Annexes, guidance material, various processes and practices established by States in order to identify issues diminishing the effectiveness and efficiency of cross-border transfers. Based on the outcomes of the review, mitigation strategies will be developed to address the identified issues.


The code developed in Annex 7 should not be confused with the ICAO Three-Letter Designator (3LD). The ICAO 3LD is an exclusive designator that, when used together with a flight number, becomes the aircraft call sign and provides aircraft distinct identification to air traffic control (ATC). ICAO approves 3LDs to enhance security and safety of the air traffic system. An ICAO 3LD may be assigned to a company, an organization or an agency and is used instead of the aircraft registration number for ATC operational and security purposes. An ICAO 3LD is also used for aircraft identification in the flight plan.

Going back to when ICAO was still PICAO, the importance of being able to identify newly created airlines in flight was already clear. The COM panel of PICAO was the group that provided the groundwork for the Three-letter and Telephony identifiers that we use today. Initially, there were only telephony designators assigned. As the number of airlines increased, it was decided that States would also make requests to ICAO to assign two-letter designators along with a telephony designator. These designators consisted of a unique two-letter code which could be used in aircraft identification in the flight plan and/or a telephony designator, which then could be used as part of an aircraft’s radiotelephony call sign. Due to the increasing number of airlines, ICAO proposed the change from the old two-Letter designator system to the current Three-Letter Designator system in November 1981. In 2019, over 5,800 designators were listed in the 3LD database.


Within the ICAO philatelic collection, one can find many stamps with aircraft reproductions bearing nationality and registration marks. A few examples are provided hereafter.



Sao Tome and Principe - 21/12/1979 - 35th Anniversary of ICAO; history of aviation, powered flight.

Spirit of St. Louis (1927) flown by Charles Lindbergh and registered in the experimental category N-X-211 in the USA (officially known as the Ryan NYP, for New York to Paris; s/n 7331); ICAO emblem.


Zambia - 26/01/1984 - 40th Anniversary of ICAO.  

de Havilland D.H.66 Hercules of Imperial Airways (circa 1931); registered G‑AAJH "City of Basra" in United Kingdom (c/n 393).


Hungary - 13/01/1994 - 50th Anniversary of ICAO.

Douglas DC‑2-120 from American Airlines (indicated DC‑3 on the stamp) registered NC14278 in USA (indicated on the upper-right wing, c/n 1311) over Jeppesen Low Altitude Enroute Chart (Budapest‑Bratislava region); 50th anniversary logo


Monaco - 17/10/1994 - 50th Anniversary of ICAO.

Eurocopter AS-350B Écureuil (Squirrel helicopter from Heli Air Monaco, registered 3A-MMC in Monaco; view of Monaco Heliport and 50th anniversary logo.


Cuba - 09/11/1994 - 50th Anniversary of ICAO.        

Douglas DC‑3 from Compañia CUBANA de Aviación S.A. and 50th anniversary logo. Registered CU-T172 in Cuba (c/n 11671).

Error: The article "la" is not needed in the Spanish name of the Organization (Organización de Aviación Civil Internacional).


Lesotho - 17/11/1994 - 50th Anniversary of ICAO 

Depicts a mosotho horseman accompanying his wife to the airport; de Havilland Canada DHC-6-300 Twin Otter from Lesotho Airways; 50th anniversary logo. Registered 7P-LAP in Lesotho (c/n 837).   

Saint Vincent and The Grenadines - 01/12/1994 - 50th Anniversary of ICAO.

Dornier Do 228-200 aircraft from the fleet operated by Air Martinique, at Bequia Airport, registered F-OGOZ in France (c/n 8161); 50th anniversary logo.


According to Annex 7 - Aircraft Nationality and Registration Marks to the ICAO Chicago Convention, an aircraft is defined as any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth’s surface. It is a generic term.

The classification of different types of aircraft is provided hereafter according to the same Annex 7:

1.         Lighter-than-air aircraft: Any aircraft supported chiefly by its buoyancy in the air. It includes:

a.         Non-power-driven balloons (free balloons, and captive or tethered balloons), and

b.        Power-driven airships.

2.        Heavier-than-air: Any aircraft deriving its lift in flight chiefly from aerodynamic forces. It includes:

a.         Non-power-driven aircraft (gliders and kites), and

b.        Power-driven aircraft (aeroplanes, rotorcrafts such as gyroplane and helicopters, and ornithopters).


Many classifications of aircraft are conceivable. On the basis of ICAO’s classification, let’s define a few words taken from Chapter 1 of Annex 7. An aeroplane or airplane is an aircraft, deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight; it is the generic term describing most heavier-than-air craft. The 19th-century French word aéroplane is made up of aéro meaning air and the Greek word planos meaning wandering.

A glider is an aircraft deriving its lift in flight chiefly from aerodynamic reactions on surfaces which remain fixed under given conditions of flight. A gyroplane is an aircraft supported in flight by the reactions of the air on one or more rotors which rotate freely on substantially vertical axes. A helicopter is an aircraft supported in flight chiefly by the reactions of the air on one or more power-driven rotors on substantially vertical axes. An ornithopter is an aircraft supported in flight chiefly by the reactions of the air on planes to which a flapping motion is imparted. A rotorcraft is an aircraft supported in flight by the reactions of the air on one or more rotors. A few examples are provided here-after.

On 21 November 1783, the first free flight carrying a human occurred in Paris, France. The Montgolfier Brothers made the balloon from paper and silk. It carried two men, Francois Pilate de Rozier and Francois Laurent, Marquis of d’Arlanders.

By the summer of 1931, Graf Zeppelin airships began regularly scheduled commercial service on the route between Germany and South America.

The site of the first gliding field in Hungary was established in the summer of 1929. The Hungarian gliding movement slowly gathered momentum in the following years.

Kite flying in China dates back to several hundred years BC and slowly spread around the world.

The Convention of the Rights of the Child, signed on 20 November 1989, was the occasion of issuing this stamp with children’s kites.


The Airbus A380 is a wide-body (called twin-aisle) aircraft manufactured by Airbus. It is the world's largest passenger airliner with its two separate aisles running from the front to the back of the passenger cabin.

Helicopter from Heli Air Monaco. A helicopter is an aircraft supported in flight chiefly by the reactions of the air on one or more power-driven rotors on substantially vertical axes.

Henri Giffard, a French engineer, invented the injector that maximized steam powered engines and the steam-powered dirigible airship in 1852. It was the world's first passenger-carrying airship (then known as a dirigible). The picture shows Giffard’s tethered massive balloon that was installed in the courtyard of the Tuileries during the Paris Word’s Fair of 1878 during which it carried 35,000 passengers.

The Spanish aviation pioneer Juan de la Cierva was the inventor of the gyroplane; it flew for the first time in January 1923. The gyroplane or gyrocopter is a type of rotorcraft that uses an unpowered rotor in free autorotation to develop lift. Forward thrust is provided independently, by an engine-driven propeller.

In 1809, the Austrian Jacob Degen had successfully flown in an ornithopter. The wings provided just enough lift to rise with the help of the balloon.