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The origin of plane registration codes

2019 marks a century since the introduction of plane registration codes. Join ACS to explore their origins and how they revolutionised the aviation industry.

A brief history of plane registration codes

The origin of plane registration codes can be traced back to 1919, when the Commission Internationale de Navigation Aerienne, (Convention for the Regulation of Air Navigation or CINA) convened for the first time following the end of the First World War. It was decided that each participating nation must select a single Roman capital letter, followed by a group of four additional capital letters, to be imprinted on registration plates so their planes could be recognised internationally. CINA stated: “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."

The British Empire selected “G” for Great Britain, while Germany chose “D” for Deutschland, France opted for “F” and Japan chose “J”. By contrast, the United States delegation was assigned “N”. The rationale behind the US’s issued letter is a contested topic with many contrasting theories. Some believe the patriotic delegates selected the letter “N” as it is the 13th letter in the alphabet, in homage to the 13 original US states. Others believe the letter “N” was selected as a tribute to the four US Navy Curtiss flying boats named NC-1 through NC-4 that attempted the first crossing of the Atlantic Ocean.

Another proposal is that, as each of the five superpowers were only allowed a single designated letter, the US couldn't be identified as “US”. But the most plausible explanation is that the unusual choice followed the lead of the US Navy, which had used “N” as its prefix call-sign to stations since 1909 in recognition of the American industry’s leading development and use of wireless communications.

International vs domestic codes

Vintage plane on runway
Vintage plane on runway

The Air Commerce Act of 1926 ushered-in the 1919 Paris Convention rules for public recognition, but these only applied to planes making international journeys. In a bid to classify domestic planes, the Air Commerce Act rejected the four Roman letters used for international planes in favour of four numbers – 0000 through 9999 – as a new national identification method. The Act also extended plane identification codes to include a letter, which would classify the plane as either Commercial (C), State (S) or Private (P). It wasn't until 1948 that the letter “N” was required on all aircraft operating within and outside US borders.

Plane registration codes today

With the technological advancements that continue to innovate and propel the aviation industry to new heights, being able to identify a plane’s whereabouts and country of origin has never been more important. Air traffic control centres around the world monitor airspace via two radar systems: primary and secondary. Primary radar was developed in the 1930s and gives an approximate location of the plane through reflected radio waves, while secondary radar automatically transmits a unique four-digit code upon receiving radio signals, and requests additional information like identity and altitude. These modern developments work in conjunction with plane registration codes to confirm the plane’s identity. All of these mechanisms help modern airline operators to reinforce aviation safety and security for personnel and passengers.

Whether you’re planning a domestic or international private jet charter, allow Air Charter Service to deal with the logistics so you can enjoy a bespoke and stress-free journey aboard your “N” branded plane. Use our simple pricing tool to receive a private jet charter quote, or for more assistance contact us online.



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