A lot of static (MMSI, name, dimensions etc) and dynamic (position, speed, course etc) information is constantly being transmitted via a vessel's AIS. However, no information on the vessel's flag is directly included in these transmissions. Still, it is possible to "decipher" the flag of any vessel using her MMSI number.
A Maritime Mobile Service Identity (MMSI) is a nine-digit number which is uniquely assigned to identify (among other stations) ship stations. Thus, every vessel has her own, unique MMSI number. This number is sent, in digital form, over a radio frequency channel and is included, as already mentioned, in the AIS-transmitted information.
The first digit of an MMSI depends on the kind of station to which it is assigned. So, MMSIs starting with any number between 2 to 7 refer to ship stations. The initial digit of a ship station determines the vessel's area of origin:
- 2 = Europe
- 3 = North America, Central America and Caribbean
- 4 = Asia
- 5 = Oceania
- 6 = Africa
- 7 = South America
The next 2 digits make each MMSI country-specific. This is how the vessel's flag can be identified! For example:
- 247 = Italy, 205 = Belgium (notice that due to the fact that these countries are European, both their MMSIs begin with the number 2)
- 316 = Canada
- 503 = Australia
- 632 = Guinea
So, the first 3 digits of any MMSI number are indicative of the respective vessel's flag. These 3 digits are also called Maritime Identification Digits (MID). Note that some countries have more than one MID assigned to them. For example:
- MIDs 237, 239, 240, 241 all refer to Greece
- MIDs 351, 352, 353, 354, 355, 356, 357, 370, 371, 372, 373 all refer to Panama
In general, an additional MID is assigned to a country in cases where the MMSIs produced using the existing MID(s) is more than 80% exhausted and the rate of assignments is such that 90% exhaustion is foreseen. This is why countries with extensive maritime activity have multiple MIDs assigned to them.
For a full table of assigned MID codes, click here.
Note that you can activate the MarineTraffic "AIS Flag Changed" Notification and be directly informed when any of the vessels that interest you the most changes her flag!