The description of PlanePlotter claims that it can determine the registration letters from the ICAO 24 bit address algorithmically for some countries.

The only thing i got so far is how to get the country. Any clues?


After some more research I found some information in the book "Principles of Avionics" by Albert Helfrick:

Generally, there is no algorithm giving a one-to-one correspondence between ICAO 24 bit addresses and the registration number of the aircraft. Some ICAO member states did have an algorithm that would translate ICAO 24 bit aircraft addresses to registration numbers but ICAO strongly suggested the practice to stop.

Algorithm for swedish registrations: http://www.transportstyrelsen.se/publicdocuments/PDF165.pdf

  • $\begingroup$ Maybe some countries have a system and the people at PlanePlotter reverse engineered them? $\endgroup$ Oct 31, 2014 at 23:48
  • $\begingroup$ Do you have a link to this claim? $\endgroup$
    – usernumber
    Oct 31, 2014 at 23:50
  • $\begingroup$ coaa.co.uk/planeplotter.htm "PlanePlotter can can determine the registration letters algorithmically, from the 24-bit hex address" $\endgroup$
    – Chris
    Oct 31, 2014 at 23:56
  • $\begingroup$ Is there anyway to tell if the aircraft is rotary or fixed wing from the ICAO 24-bit address? $\endgroup$
    – wittrup
    Sep 11, 2015 at 0:03
  • $\begingroup$ Hi @Chris: The edit in the question IMO should be an answer; feel free to submit it as an answer, self-answering is encouraged here. And personally I'd bold emphasize the "ICAO strongly suggested the practice to stop" part. $\endgroup$
    – user14897
    Aug 21, 2021 at 17:52

3 Answers 3


Apparently (according to these folks) some countries use an algorithm to generate their ICAO (Mode S) 24-bit IDs. For those countries, you can simply reverse the algorithm and get a registration given the Mode S ID.

Others countries allow you to download their registration database, complete with the Mode S identifier (you can get the US registration database here) - it's a simple matter to load this into your own software and map the ICAO/Mode S ID code to a registration number.

As the folks at Gatwick Aviation Society have noted, some countries are tight-lipped about how their codes are assigned (and who they're assigned to), so these lookups are probably not complete.


The Mode_S closed-group on Yahoo Groups has documented many of the allocation algorithms.


Apply to join and explain your motivations. They have an extensive Files section.

  • $\begingroup$ There are no algorithms documented in the Files section of that group that I can find, only lists of <ICAO>,<algorithmically generated registration #> $\endgroup$ Apr 25, 2016 at 15:04
  • $\begingroup$ Not only are there no algorithms in that Files listing, but the listing for Belgium is very incomplete and contains lots of tail codes that are not even allowed - all the ones starting with Q for example. $\endgroup$
    – Petoetje59
    May 6, 2016 at 13:03

Some countries use a deterministic formula (e.g. US, Japan, South Korea), others use do not. There are about a dozen or two that do have a formula. Take a look at the popular ADS-B decoder dump1090's decoding logic.


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