MMSI identity format
AIS-SART MMSI (970xxyyyy)
An MMSI in the form 970xxyyyy identifies a ais-sart (search and rescue transmitter). 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 970 prefix identifies an AIS search-and-rescue transmitter (AIS-SART): a battery-powered locating device carried in survival craft and switched on after abandoning ship. It broadcasts a position so nearby ships and aircraft can find the survivors.
How to read it
A live AIS-SART is a distress signal from a life-raft, not a vessel. Its digits identify the device maker and a serial number, not a country. Distress is handled by rescue coordination centres on official channels — never act on it from this site.
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.