These rules were written up by Andreas Gehrs-Pahl, schnars@ais.org.

US Registration numbers: Rules (see FAR 47.15(b)): The rules for registration numbers of aircraft in the USA are:
Description:

Form: N[c][-]n[n][n][X][X]
										see : 1 2  3 4 5  6  7  8
										

1. N (international prefix: USA)
2. C/L/R/X (Category, mostly omitted)
3. - (dash, mostly omitted)
4. digit (1 to 9)
5. digit (0 to 9 or nothing)
6. digit (0 to 9 or nothing)
7. character (0 to 9, A to H, J - N, P - Z or nothing)
8. character (0 to 9, A to H, J - N, P - Z or nothing)

min.: N1
max.: NX-999ZZ

1) International Prefix:

N (for USA)

2) Category:

Not part of the Registration nor the Prefix, but is sometimes displayed on the aircraft (especially before 1950s):

• C = Standard,
• L = Limited,
• R = Restricted,
• X = eXperimental.

3) Separator:

The dash (-) or a space ( ) as a Seperator between Prefix and Registration is in most cases omitted.

4-8) Registration:

1 to 5 characters, allowed are digits (0 - 9) and letters (A - H, J - N, P - Z), exempt are I and O, to not be confused with the digits 1 or 0. The registration can be split into two categories:

1. numeric: 1 to 5 digits (N1 to N99999)
2. alphanumeric: (here I have to use examples to be 100% clear):

   1A - 9999A (9999 registrations)

   ...

   1Z - 9999Z (for all 24 allowed characters)

   and

   1AA - 999AA (999 registrations)

   ...

   1ZZ - 999ZZ (for all 24*24 allowed combinations)

Summary: N plus 1 to 5 characters (usually without a dash '-', sometimes with a category letter; first character is always a digit from 1 to 9; can be followed by up to 4 more digits and can end with up to 2 letters, but letters can not be followed by digits; the characters I and O are not allowed; no other rules exist, concerning:

• military/government ownership,
• special purpose/prototype/evaluation,
• aircraft type, or
• location.

Remarks: A total of 99,999 + 9999 * 24 + 999 * 24 * 24 = 915,399 aircraft could be registered at any given time. (The 1990/91 FAA database contains about 300,000 registrations). NASA owned aircraft have mostly registrations of the form NxxxNA, were xxx is a number from 1 to 999. This is not a rule, and this is not a NASA specific registration form. Government owned special purpose aircraft (like CIA operated U-2s) sometimes use 'fake' registrations, which are not in the register, or fly without any registrations. Without a civil registration, it is difficult to get overflight or landing rights from any other country.

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German Registration Numbers Rules: The rules for registration numbers of aircraft in Germany have to be divided into 3 time frames:

1. pre-1945 - Germany (Deutschland, Deutsches Reich, etc.)
2. 1945 - 1990 - German Republics
   1. 1955 - 1990 - West Germany (Bundesrepublik Deutschland)
   2. 1952 - 1990 - East Germany (Deutsche Demokratische Republik, DDR)
      1. 1952 - 1956 (International Prefix DDR)
      2. 1956 - 1981 (International Prefix DM)
      3. 1981 - 1990 (International Prefix DDR)
3. 1990 onwards - Germany (Bundesrepublik Deutschland)

This description covers time frames 2a) and 3) - post-W.W.II (West) Germany:

Description:

Form: D-XXXX
										see : 123456
										

1. D (international prefix: D)
2. - (dash, sometimes omitted, usually not)
3. character (0 to 9 or A - C, E - I, K - M, O)
4. character (0 to 9 or A - Z)
5. character (0 to 9 or A - Z)
6. character (0 to 9 or A - Z)

min.: D-0001
max.: D-OZZZ

1) International Prefix: D (for Deutschland)

2) Separator: The dash (-) as Seperator of Prefix and Registration is usually displayed.

3-6) Registration: 4 characters, allowed are digits (0 - 9) and letters (A - Z). The registration can be split into two main categories:

1. numeric: 4 digits (D-0001 to D9999) for:
   • sailplanes/glider have registrations of this form;
   • the block 9500 to 9999 was reserved for some semi-military, government owned, aircraft during the 1960s;
2. letter: (4 letters D-xAAA - D-xZZZ), where x stands for one of the following aircraft type categories:

   A - multi-engine, MTOW >20,000 kg,

   B - multi-engine, MTOM >14,000 kg - 20,000 kg,

   C - multi-engine, MTOW >5,700 kg - 14,000 kg,

   E - single-engine, MTOW <=2,000 kg,

   F - single-engine, MTOW >2,000 kg - 5,700 kg,

   G - multi-engine, MTOW <=2,000 kg,

   H - all rotory-wing, (Hubschrauber = helicopter)

   I - multi-engine, MTOW >2,000 kg - 5,700 kg,

   K - all powered gliders,

   L - all airships, (Luftschiff = airship)

   M - all ultra lights, (UL)

   O - all manned free balloons,

   the categories D, J, N, P - Z are not used (at this time).

Summary: D- plus 4 characters; either 4 digits (for sailplanes/glider) or 4 letters; if letter, the first letter depicts aircraft type category; some military/prototype aircraft were registered in the D-9500 to D-9999 series during the 1960s; no other rules exist, concerning:

• special purpose/prototype/evaluation,
• location.

Remarks: A total of 9999 sailplanes/glider and 26 * 26 * 26 = 17,576 aircraft in each other type category could be registered at any given time. There are not many civil registered 'war-birds' in Germany, because private individuals are not allowed to possess any armed or ex- military aircraft (exceptions exist). There are some W.W.II era aircraft, like a Ju-52/3m owned by Lufthansa Traditionsflug (a transport plane), and the MBB (now Daimler-Benz Aerospace) owned Me 109, but those are company-owned and not private aircraft.