recent query to the American Aviation Historical Society (www.aahs-online.org)
asked the question, "What is the origin of the "N" in
United States civil aircraft registrations?"
How did the U.S. end up with "N" instead of
"US," or some other designation, as the prefix on our civilian
aircraft? After all, Sweden
has "SE", Great Britain uses "G", Germany has
"D" (Deutschland), and France is "F".
And while we are considering this question, where do the C, L, R,
X and S prefix designations (NC12345, NX123B, NS123) as seen on some
aircraft come from?
Commission Internationale de Navigation Aerienne
origins of the N in the U.S. registration can be traced back to the
Commission Internationale de Navigation Aerienne (CINA - the Convention
for the Regulation of Air Navigation) established as part of the Paris
Peace Conference immediately following World War I. A part of this
conference was the adoption of the Convention for the Regulation of
Air Navigation that laid the foundation of the system of
international aircraft identification still in use today.
In these proceedings, the first letter(s) of the identification
designating national origin are set as in the examples described above.
Each major participating country was allowed a single identifying
letter and to specify their own designation letter.
The U.S. delegation was allocated "N."
The convention stated that:
nationality mark shall be represented by capital letters in Roman
characters. The registration mark shall be represented by a group of
four capital letters; each group shall contain at least one vowel, and
for this purpose the letter Y shall be considered a vowel. The
complete group of five letters shall be used as a call sign for the
particular aircraft in making or receiving signals by wireless
telegraphy or other methods of communication, except when opening
up communications by means of visual signals."
The nationality and registration marks are assigned in accordance with
the exact rationale for selecting the letter "N" has not been
preserved, there are a number of stories as to why N was chosen.
Some might be classified as "wives tales," others
seem to have a grain of truth to them. Though none have been
substantiated, here are a few reasons that have been uncovered.
Lindberghs Spirit of St. Louis displays
an X registration number
on the Ryan NYP (New York - Paris) indicating that
it was registered in the Experimental category
in April 1927. As the
aircraft was not a production design, the NX-211registration would have
been consistent with the regulations. The
problem is that the use of X for Experimental
was not officially adopted
until 1929! (Photo from the Don Hall collection)
TBM-3E Avenger seen
in Palm Springs in 2001, still carries its original Limited
NL registration, even though
the use of the L was
dropped in 1948. (Photo from C.H. Hamilton collection)
As do many
aircraft from the Golden Age of flying, this Waco SRE, s/n 5153, NC1252W
seen at the 1995 EAA Convention in Oshkosh, Wis., still sports an NC
registration number. The CAA dropped the use of the C, L, R, and X
registration identifiers in 1948, replacing all but the C with
cockpit placards. (Photo by Al Hansen)
"N" Version 1
As early as 1914, states
began to license airplanes based in their states.
This was partly motivated by the prospects of increasing the
state's coffers through the associated licensing fees with public
justification being easy identification of aircraft being operated in a
way that put life and property at risk.
States pursuing this aircraft licensing direction tended to
follow their existing licensing practices for personal watercraft. Maryland was the first state to enact aircraft licensing
requirements sometime in late 1914.
The first aircraft license issued was MAR-1.
Other states soon followed and generally used some sort of
shortened alpha character followed by numbers.
U.S. delegates attending the Paris
Conference and working on the Convention for the Regulation of Air
Navigation were aware of the individual state's licensing efforts.
In an attempt to avoid confusion with the display of a required
state identification number, this group appears to have requested the
letter N that it deemed would stand for the national number.
As to the issue of avoiding confusion?
A quick check of state names shows that states with names
beginning in N are among the most prolific.
If we assume that these states would use N as part of their state
registration identifier, then the selection of N for a national
identifier would only add to the confusion.
With Utah being the only state beginning with U, this would
have been a more logical choice based on this rationale.
Furthermore, this letter was not assigned at the 1919 conference,
so was readily available.
"N" Version 2
The delegates, being very
patriotic selected the letter N in recognition of the thirteen
original states that formed the U.S.
N was selected because it is the thirteenth letter in the
Now one can just imagine a bunch of
bureaucrats sitting around a table - probably after having consumed
copious amounts of alcohol - coming up with this rationale.
The only problem is that the letter N is the fourteenth
letter in the alphabet. So
what letter was excluded? Or,
did these individuals just not have a firm grip on the alphabet.
This version is probably best categorized as an interesting story
but not the real reason N was selected.
"N" Version 3
This version is based on current
events of the time. The four U.S. Navy Curtiss flying boats (designated NC-1 thru
NC-4) set out on May 14, 1919, to begin the first crossing of the
Atlantic by an aircraft. As
we know, only NC-4 successfully completed this crossing, eventually
arriving in Plymouth, England, on May 27, 1919.
This first flight (albeit not nonstop) preceded the nonstop
flight by Alcock and Brown by almost a month.
The flight was still fresh on everyone's mind at the time the
first international aviation congress convened and our delegation
selected N in commemoration of this first flight.
This story sounds logical,
particularly if none of the U.S. delegates were Navy types and were
unaware that the N designation for the NC-4 really stood for Navy.
This story like the others has not been substantiated.
"N" Version 4
The letter N was
selected to stand for North America, with C being assigned to
Central America and S for South America.
The U.S. ended up exclusively with N because Canada was
part of the British Empire in 1919 and the registration convention for
such colonies was to use the British designation in combination with an
assigned letter. Canada's
designation was G-Cxxx which was changed later.
Along with this story goes the postulation that the letters
"US" or "USA" could not be selected because the U.S.
was one of the five "super" powers designated to have only a
single registration prefix. The letter U was unacceptable for unknown reasons, even
though it was not assigned to any country during the 1919 convention.
The problem with this version is
that it is rife with inconsistencies.
As we can see in Table 1, the list of assigned registration
letters to all the 1919 participants, Brazil was given P-Bxxx and Panama
S-Pxxx, neither of which is consistent with this theory.
In fact, a quick scan will show you other inconsistencies as
well. Furthermore, Great
Britain was quite content with the single letter G; so the U.S.
could have just as easily accepted U.
"N" Version 5
The most probable reason the
U.S. was allocated N for its national registration mark comes from
existing regulations of wireless communications in place in 1919.
The International Telecommunications Union (ITU, formed in the
late 1800s to provide international standards in telecommunications and
still going strong today) held its first International Wireless
Telegraph Conference in Berlin in 1906.
Here the first Service Regulations were established for
governing international radiotelegraphic communications.
It was at this conference that S-O-S was adopted as the
international radio distress call.
By 1912, the proliferation of wireless radio stations, both land
and ship based, had created chaos in the airways as each base (or
country) was creating their own call-signs for identification leading to
the potential for call-sign duplication.
In 1912 at the London International Radiotelegraphic Conference,
the Service Regulations were expanded to include a protocol for
international radio call-signs. In
short, the following identifiers where assigned to major countries:
G - Great Britain
D - Germany
F - France
I - Italy
J - Japan
N, KDA-KZZ, Wxx - United States
reason "N" was assigned to the U.S. was in recognition of the
industry leading development and deployment of wireless communications
by the U.S. Navy that had been using "N" as the prefix to its
station call-sign identifiers since 1909.
Obviously, at this point in history
(1912) aircraft were barely capable of carrying a pilot and passenger,
much less a bulky wireless set. By 1919, when the CINA met, both aviation and wireless
technology had made great advances - in part due to developments
associated with WWI. Aircraft
were now capable of carrying wireless communication gear and the
practice of including such gear was increasing.
As an international protocol for identifying wireless stations
already existed, the CINA simply adopted a subset of the ITU call-sign
identifiers for consistency. Support
of this can be seen in the CINA specifications quoted above that state
aircraft are to use their registration number in wireless communications
with base stations. By combining the ITU standards into the registration marks,
the CINA was simply assuring clarity in wireless communication on an
international basis while avoiding unnecessary redundancy.
Support for this version is found
in Aviation magazine dated June 11, 1923 (page 639) that states:
Mark of American Aircraft: Aviation reported some time ago on the
strength of a Norwegian government decree published in "Machrichten
fur Luftfahrer" (the German air department bulletin) that Norway
had adopted the letter "N" as its nationality mark. As this
letter had previously been allotted to the United States as its aircraft
nationality mark, it was editorially suggested that when this country
becomes a party to the International Air Convention, the American
representatives should ask to have the letter "W" allotted as
our aircraft nationality mark. It was pointed out that as the letter
"W" was one of the international call letters allotted the
United States - as is "N" - such a choice would be
eminently practical as well as an act of homage to the Wright brothers.
The National Aeronautic Association of U.S.A. now announces on the
authority of the Controller General of Civil Aviation in Canada that at
the third session of the International Commission for Air Navigation,
the letter "E" was granted to Norway as that country's
nationality mark, with the letter "N" as the first letter of
the registration mark. The letter "N" therefore remains the
nationality mark allotted to United States civil aircraft." [Norway
never adopted the E-Nxxx allotted to it, but later standardized on
article tends to support the supposition that the CINA adopted the ITU
call-sign identifications as both N and W appear to have
been allocated to the U.S. The article also implies that we quite easily
could have ended up with our aircraft registration numbers beginning
with W, though not in honor of the Wright brothers.
Unfortunately, the U.S. Department
of Commerce Bureau of Navigation (responsible of administering wireless
radio communications from 1911-1927 didn't get with the program.
They continued to require separate radio licenses in planes so
equipped. During the 1920s and 1930s, they even issued separate
call-sign identifiers to these stations beginning with the letter K. For
example, in 1937 Amelia Earharts call-sign on her Lockheed 10E,
NR16020, was KAHQQ. It was
not until the late 1940s that the practice of assigning call-signs was
discontinued, though they still required a radio license for both the
radio transmitter and the operator.
So, we can probably thank,
indirectly, the U.S. Navy for the "N" in the U.S. aircraft
registration, as some have postulated, but it wasn't because of the
transatlantic crossing of the Navy-Curtiss flying boats.
Interestingly enough, the
U.S. Government would not ratify the 1919 accord. It wasn't until 1926
that the issue of national aircraft registration had reached a point of
visibility that forced Congress to finally act in the form of the Air
Commerce Act of 1926. In
the meantime, in 1921, the National Aircraft Underwriters Association, a
service organization for the insurance industry, attempted to establish
a five-letter licensing code. The
code included the prefix letter N followed by four alpha
characters (N-ABCD) in a manner similar to that currently used by a
number of countries including Great Britain (G-ABCD).
This system was purely voluntary and had no governmental backing
or support. Due to a lack of support from either the government or by
manufacturers, only 33 planes were registered by the end of 1922.
The system had been abandoned by 1925.
While the exact number of aircraft registered with this system
probably never exceeded 50, there are aircraft from this period that
appeared with registrations in this form.
In May 1926, the Federal Government finally got its act together with
its first attempt at organization via the Air Commerce Act that
became effective in January 1, 1927.
This system essentially implemented the 1919 Paris Convention
relative to national identification, but deviated in that the
identifying marks would be numbers 0000 through 9999 rather than four
Roman letters. It further extended the system by including a classification
letter to denote commercial (C), State (S), or private (P).
The letter C was used to designate approved (airworthy)
aircraft used in commerce and for airmail.
The S included all state and federal government owned and
operated aircraft. The P designation was created to sort out
private aircraft from the C and S types, but this lasted
only until March 1927. The
need for the P designation was obviated by most states requiring
aircraft operating within their boundaries to bear a C number.
Interestingly enough, Oregon where much flying activity took
place, was one of the few exceptions to this requirement.
From the implementation of the Air Commerce Act until the
late 1930s, the aircraft registration actually consisted of two parts
the Identification Mark Assignment number, and if approved
for any form of formal license, the prefixes. A limit of four numbers
was deemed adequate at the time to handle all possible aircraft
registrations - after all, who in 1926 could imagine an aircraft
population numbering more than 10,000?
By November 10, 1928, less than two
years from the time the DoC started issuing licenses and Identification
Mark Assignments, the 10,000th number had been issued and the DoC
ruled that, since issuance of numbers above 9,999 would
"unnecessarily incumber the wings of planes, a reissue has been
started with the addition of a capital letter "E" following
A provision in the 1926 Act also
allowed for identification of aircraft that did not meet minimum
airworthiness requirements. These aircraft were termed Identified
Aircraft and were to wear Identification Mark Assignment (IMA)
numbers, usually without the N. It
was possible to register such aircraft under this provision up until
The National Air and Space Museum (NASM)
has an on-going Pre-1946 U.S. Civil Aircraft Register Project.
In their research of the Department of Commerce records, the
earliest document found specifically referring to aircraft markings in a
registration file was dated April 20, 1927, when the Department of
Commerce sent a letter to the Ludington Exhibition Co., Inc., in
Philadelphia. The letter
states, in part,
herewith is your "Identification Mark Assignment" together
with a metal identification plate. The identification mark which has
been assigned to you must be prominently displayed on your aircraft in
accordance with the provisions of Section 41 of the Air Commerce
Regulations. The metal plate must be permanently affixed to the fuselage
in a prominent place, in order that it may be readily inspected. No
letter or other mark or symbol of any kind shall immediately precede or
follow the identification mark thus displayed on your aircraft.
first commercial aircraft license issued in the United States was C-26,
issued to Wendrell Pavey of Madison & Edwards Roads, Cincinnati,
Ohio, for a Standard J-1. At this point in time, the Department of
Commerce was actually issuing metal plates with both the IMA and
Manufacturers Serial Numbers (or substitute numbers, if none existed),
although this practice quickly came to an end, and the CAA required
manufacturers or builders to affix permanent data plates.
The requirement for the display of the N portion of the
identification number was only required on aircraft being operated
internationally. If the
aircraft was locally based and operated, it was only required to display
the C, S or P number. It is possible to locate
aircraft photographs from this period in which the N is not
displayed, though this practice appears to be the exception rather than
the rule. The requirement to use N on aircraft operated within
U.S. boundaries did not come about until 1948.
In 1929, the Air Commerce Act
was amended to modify the identification number convention.
Under the new plan, a combination of three numbers and an alpha
suffix of: E, H, K, M, N, V, W, or Y was approved.
This new block of identification numbers were consumed by the end
of 1934! Class prefixes
were expanded to include R for restricted and X for
experimental aircraft. A class prefix of G for gliders was implemented as
well. This class prefix was
canceled in 1937 when sailplanes and gliders were placed in the same
class as powered aircraft. The
S class for government-owned aircraft was also dropped in 1937.
September 1, 1929, the DoC recognized the need to refine their
procedures. They acknowledged, in a document issued that date, that
"some confusion exists amongst owners as to the privilege of using
the international symbol "N" on aircraft, licenses will be
issued to cover international operation, except in accordance with Air
Commerce Regulations, effective September 1, 1929, planes licensed for
experimental purposes shall not display the letter "N".
Hereafter, licenses (other than experimental) will not be issued as
C-100, or R-100, but as NC-100 or NR-100, etc. Owners of planes, except
experimental, may paint the international symbol "N" on the
wings and tail for operation in the United States, but will not be
required to do so. The symbol, however, must be applied before the plane
is operated either temporarily or regularly in a foreign country."
This rule was later amended and the prefix "NC-" became
standard. It is important to note that the "dash" character
was regarded as a part of the registration. The Civil Aeronautics
Authority (CAA) continued to adhere to this policy as late as July 1934.
On August 14, 1933, the CAA took a
policy stance with regard to numbers issued to aircraft. Up until the
post-World War II surplus boom, they were remarkably religious about
issuing one and only one number for each aircraft built. In the August
1933 document they went so far as to state "the Department has
consistently refused to assign new numbers to aircraft when there has
been sufficient identification, of even salvaged aircraft, to connect it
with some aircraft of which we have a record, and to which a number has
been previously assigned." Had they adhered to this rule, life
would have been much simpler for generations of aviation historians and
researchers that followed!
In 1935, visionaries stepped in with claims that increasing registration
numbers from four to five numerals, increasing the block from 10000 to
99999, would provide a more than adequate number of identification
even these were beginning to show signs of being gobbled up by the
beginning of World War II. The
responsibility of administering aircraft identification registrations
passed to the Civil Aeronautics Administration portion of the CAA that
was formed in 1938. The CAA
expanded the registration structure in 1946 to include three and four
numerals with other letter suffixes - the letters I and O
were excluded to eliminate possible confusion with the numbers 1 and 0.
The block of numbers from 46000 to 79999 was generally reserved
for war-surplus aircraft. The class prefix of L for limited type
certification was also created but lasted only until 1948.
By December 9, 1938, the last of
the formerly Identified aircraft (primarily older aircraft for
which no ATC has been issued, homebuilt, and aircraft not intended to be
operated outside the confines of the state in which they were domiciled)
had been attrited. However, when an classified aircraft did not pass
inspection, the CAA came up with a new convention for covering these.
They would order the removal of the "C" from the
"NC-" prefix, and thus the aircraft would become N-11471. This
has led many researchers on a merry chase. These were not licenses at
this point; they were Identification Marks.
The class prefixes of C,
R, X and L were eliminated by amendment to the Civil
Aeronautics Regulations (CARs) on June 14, 1948, with only the N
being used. By 1953 the
need to expand the available number of registration slots caused a rule
change to include double alpha suffixes with up to three numerals.
The letters R, X and L were replaced in 1948
with the requirement of a Restricted, Experimental, or Limited
sign be prominently displayed at the cockpit entrance. This applied to
all new registration issued after December 31, 1948. Recertification of
aircraft in the "NL" category, which was defined as military
aircraft modified for limited civil use, was extended after an August
31, 1948 deadline - mainly to accommodate air racer owners at the
Cleveland Air Races. The CARs extended the deadline to remove the
"C", "R", "X", or "L" characters
to January 1, 1951.
the Fun Begins
What really makes all of
this challenging is that none of these rules appear to be cast in stone
and examples of exceptions abound. For example, it is possible today to find examples of many of
these particular rules. At
air shows one can see Golden Age era aircraft with NC registrations, and
war birds sporting NL and NX registration identifiers.
Even the Federal Government does
not follow their own specifications.
The Federal Government initially reserved identification numbers
1 through 26 for their aircraft. This
was later expanded to 1 through 300. The original N1 designation was
assigned to a Department of Commerce de Havilland DH-4.
This aircraft wore the N1 registration even though to conform to
its owner's rules it should have carried the identification of NS1.
Because of the Department of
Commerce's practice of reassigning numbers after the sale, export or
destruction of an aircraft, the N1 number also shows up later on a
government Northrop Alpha 2, a Ford 5-AT, a Lockheed 12-A, a Douglas
DC-3 and is currently on a Gulfstream G-IV.
Furthermore, you can find private aircraft sporting registration
numbers in this designated range (N2 and N3 are registered to Cessna
Commercial Aviation Finance Corporation, but possibly leased to the
Since World War II, special request
registrations became popular leading to a proliferation of low-number
plus suffix registrations. For
a fee, one could have just about anything as long as it was available.
The CAA provided regional offices with batch allocations for
distribution to add to the confusion.
All of these practices have
combined to make using the aircraft registration number a crude
reference tool. An N
number alone is often insufficient to determine the particulars of an
aircraft. Though many
aircraft have retained their original registration number through the
years, a large number of these registrations have also been reallocated
or simply changed with change of ownership.
The First National Registrations
Civil registrations using the Underwriters
Laboratories all-letter system, 1921 to 1923:
N-AABA - Colonial Air
N-AABB - Colonial Air
N-AABC - Colonial Air
N-ABCA - John M
Larsen, New York
N-ABCB - LMC Drilling
N-ABCC - Akers
Airphoto Corporation, Chicago
N-ABCD - Ninimo Black
Chicago (Laird Swallow)
N-ABCE - John A
N-ABCF - Loening Aero
Corporation, New York (Loening
N-ABCG - Diggins
Aviation Company, Chicago
N-ABCH - Diggins
Aviation Company, Chicago
N-ABCI - Aero Club of
N-ABCJ - John C
N-ABCK - David L
Behncke, Forest Park IL
N-ABCL - David L
Behncke, Forest Park IL
N-ABCM - E Hamilton
N-ABCN - A W
Stephenson, Miles City MT
N-ABCO - Chicago
N-ABCP - Brooks, Banks
& Smith Corp,
Framingham, MA (Avro 504K)
N-ABCQ - C E Lessong,
N-ABCR - R S Thompson,
N-ABCS - Northbird
Ketchikan, AK (Curtiss MF)
N-ABCT - H P Ayres,
N-ABCU - Vincent
Astor, New York
(Loening Air Yacht)
N-ABCV - Harold S
Vanderbilt, New York
(Loening Air Yacht)
N-ABCX - Mrs K LaParle,
N-ABCW - George E
N-ABCY - Triangle
N-ABCZ - Continental
(Judson-Kantner F Boat)
N-ABDA - B D Burley,
N-ABEA - L B Coombs,
N-ABFA - E P
(de Havilland DH-4)
N-ABGA - J Sorenson,
N-ABHA - T J Junker,
El Dorado KS
N-ABIA - G Mosny Jr,
Indiana Harbor IN
N-ABJA - R R Ferguson,
N-ABKA - Anna M
Parker, Hazelcrest IL
N-ABLA - American
N-ABMA - Antone Brotz,
N-ABNA - Edward
N-ABOA - Great Lakes
Aviation Co, Cleveland
N-ABPA - Antone Brotz,
N-ABQA - W F Bridgeman,
N-ABSA - Victor Dallin
N-AFOR - Stout
Airplane Co, Detroit
(Stout Air Pullman)
N-BMUL - R W
N-CAED - Spanish River
Pulp & Paper Co,
Ontario, Canada (Dayton-Wright
N-MAAB - William Eaton
(Travel Air C-6)
N-XAAA - Walter
Becker, Newark NJ
(de Havilland DH-6)