An aircraft registration is a unique alphanumeric string that identifies an aircraft, in similar fashion to a licence plate on an automobile. In accordance with the Convention on International Civil Aviation all aircraft must be registered with a national authority (such as the FAA or Transport Canada), and furthermore, they must carry proof of this registration in the form of a legal document called a Certificate of Registration at all times when in operation. Most countries also require the aircraft registration to be imprinted on a permanent fireproof plate mounted on the fuselage for the purposes of post-fire/post-crash aircraft accident investigation.
Because airplanes typically display their registration numbers on the aft fuselage just forward of the tail, in earlier times more often on the tail itself, the registration is often referred to as the "tail number". In the United States, the registration number is also referred to as an "N-number", as it starts with the letter N.
Although each aircraft registration is unique, some, but not all countries allow it to be re-used when the current aircraft has been sold, destroyed or retired. For example N3794N is currently assigned to a Mooney M20F. It had been previously assigned to a Beechcraft Bonanza (specifically, the aircraft in which Buddy Holly was killed). Also note that individual aircraft may be assigned different registrations during its existence. This can be either the aircraft changes ownership, state of registration changes or in some countries like the United States for vanity reasons.
The Certificate of Registration contains contact information used by national authorities for enforcement purposes, and for the purposes of disseminating Airworthiness Directives to aircraft owners. Most national authorities require that the aircraft owner update said contact information immediately or as soon as possible any time there is a change in the same.
for information about registering aircraft ELTs.
The first use of aircraft registrations was based on the radio callsigns allocated at the London International Radiotelegraphic Conference in 1913. This was modified by agreement by the International Bureau at Berne and published on April 23 1913. Although initial allocations were not specifically for aircraft but for any radio user, the International Air Navigation Convention held in Paris in 1919 made allocations specifically for aircraft registrations based on the 1913 callsign list. The agreement stipulated that the nationality marks were to be followed by a hyphen then a group of four letters that must include a vowel (and for the convention Y was considered to be a vowel).
At the International Radiotelegraph Convention at Washington in 1927 the list of markings was revised and adopted from 1928, these allocations are the basis of the currently used registrations. The marking have been amended and added to over the years and the allocations and standard are managed by the International Civil Aviation Organization (ICAO).
Article 20 of the Chicago Convention on International Civil Aviation requires that all signatory countries register aircraft over a certain weight with a national aviation authority. Upon registration, the aircraft receives its unique "registration" which must be displayed prominently on the aircraft.
Annex 7 to the Convention on International Civil Aviation describes the definitions, location, and measurement of nationality and registration marks. The aircraft registration is made up of a prefix selected from the country's callsign prefix allocated by the International Telecommunication Union (ITU) (making the registration a quick way of determining the country of origin) and the registration suffix. Depending on the country of registration, this suffix is a numeric or alphanumeric code and consists of one to five digits or characters respectively.
The ICAO provides a supplement to Annex 7 which provides an updated list of approved Nationality and Common Marks used by various countries.
When painted on the fuselage, the prefix and suffix are separated by a dash (for example YR-BMA), however when entered in a flight plan, the dash is omitted (for example YRBMA). In the United States, the prefix and suffix are painted without a dash. Private aircraft usually use their registration as their radio callsign, but most commercial aircraft use the ICAO airline designator or a company callsign. In some instances, it may be sufficient to simply display the suffix letters, with the country prefix omitted. For example, gliders registered in Australia would omit the VH prefix and simply display the suffix. Obviously this is only suitable where the aircraft does not fly in the airspace of another country.
Even if the suffix consists solely of alphabetical characters in a certain country, gliders and ultralights may sometimes use digits instead. For example, in Germany, D-ABCD can be an aircraft while D-1234 is a glider. In Australia, early glider registration suffixes began with the letter "G", and it is not uncommon to find such gliders only displaying the last two letters of the suffix, as they lacked the range to travel internationally. For example, VH-GIQ would simply be displayed as IQ.
Different countries have different registration schemes: Canadian registrations start with C, British with G, German with D, and so forth. A comprehensive list is tabulated below.
Since the early years of civil aviation, aircraft registration schemes beginning with "G" has been assigned to the United Kingdom, while the "V" series have been reserved for the rest of the British Empire: VH for Australia, VT for India, VR and later VP for the colonies, and so on.
The impact of decolonisation on aircraft registration schemes have varied from place to place. After the split of the Raj, India retains its VT designation, while Pakistan adopts a completely new AP designation. Hong Kong, which formerly used the VR-H designation, had the "VR" replaced with the Chinese "B" upon the 1997 Handover to China, resulting in aircraft designations with only four letters in total (as opposed to the international norm of five letters).
An N-number is an aircraft registration number used in the United States. All aircraft registered there have a number starting with N. An alpha-numeric system is used due to the large numbers of aircraft registered in the United States. N-numbers may only consist of 1 to 5 characters and must start with a number other than zero and can not end in more than two letters. In addition, N-numbers may not contain the letters I or O, due to their close similarity with the numbers 1 and 0.[1]
Each alphabetic character in the suffix can have one of 24 discrete values, while each numeric digit can be one of 10, except the first, which can take on only nine values. This yields a total of 915,399 possible registration numbers in the namespace, though certain combinations are reserved either for government use or for other special purposes.[1]
The following are the combinations that could be used:
An older aircraft (registered before 31 December 1948) may have a second letter in its identifier, identifying the category of aircraft. This additional letter is not actually part of the aircraft identification (e.g. NC12345 is the same registration as N12345). Aircraft category letters have not been included on any registration numbers issued since 1 January 1949, but they still appear on antique aircraft for authenticity purposes. The categories were:
For example, N-X-211, the Ryan NYP aircraft flown by Charles Lindbergh as the Spirit of St. Louis, was registered in the experimental category.
| Country / Region | Registration Prefix | Suffix Pattern |
|---|---|---|
| Belgium | O-B | O-Babc |
| Bolivia | C-B | C-Babc |
| Brazil | P-B | P-Babc |
| British Empire | G | G-abcd |
| China | X-C | X-Cabc |
| Cuba | C-C | C-Cabc |
| Czecho-Slovakia | L-B | L-Babc |
| Ecuador | E-E | E-Eabc |
| Finland | K-S | K-Sabc |
| France | F | F-abcd |
| Greece | S-G | S-Gabc |
| Guatemala | L-G | L-Gabc |
| Haiti | H-H | H-Habc |
| Hedjaz | A-H | A-Habc |
| Honduras | X-H | X-Habc |
| Italy | I | I-abcd |
| Japan | J | J-abcd |
| Liberia | L-L | L-Labc |
| Panama | S-P | S-Pabc |
| Peru | O-P | O-Pabc |
| Poland | P-P | P-Pabc |
| Portugal | C-P | C-Pabc |
| Romania | C-R | C-Rabc |
| Serbia-Croatia-Slavonia | X-S | X-Sabc |
| Siam | H-S | H-Sabc |
| United States of America | N | N-abcd |
| Uruguay | C-U | C-Uabc |