MMSI identity format
Man-overboard device MMSI (972xxyyyy)
An MMSI in the form 972xxyyyy identifies a man-overboard device. How to recognise it, where its country digits sit, and why reading the first three digits as a flag would be wrong.
What it identifies
A 972 prefix identifies an AIS man-overboard (MOB) device: a small beacon worn on a lifejacket that transmits the position of a person in the water.
How to read it
A live 972 identity is a person, not a boat. As with AIS-SARTs, the digits name a manufacturer and serial, not a flag.
Does it give a flag?
No — the format carries no MID at all.
Every vessel page on this site works this out before printing a flag. Where the MMSI is not a ship station, the page names the kind of station instead — a wrong flag is worse than an honest “this is a coast station”.
All MMSI formats
| Pattern | Station |
|---|---|
| MIDxxxxxx | Ship station |
| 00MIDxxxx | Coast station |
| 0MIDxxxxx | Group of ships |
| 111MIDxxx | SAR aircraft |
| 99MIDxxxx | Aid to navigation |
| 98MIDxxxx | Craft associated with a parent ship |
| 970xxyyyy | AIS-SART (search and rescue transmitter) |
| 972xxyyyy | Man-overboard device |
| 974xxyyyy | EPIRB with AIS |
| 8MIDxxxxx | Handheld VHF with DSC and GNSS |
Have a number to check? The MMSI decoder applies these rules to any nine digits. For the background, read Reading an MMSI.