Thanks.

The url is www.icao.int

The relevant material is difficult to locate in available documents for someone not familiar with this but what I have been able to understand is that the protocol for communication via a satellite from an aircraft is an adaptation of the GSM protocol from telephony and the satellite is basically the equivalent of a cell tower for the aircraft.

If this is the case, then the aircraft equipment would likely have the equivalent of the IMEI to identify the equipment and IMSI to identify the subscriber.

What I do not know is whether the communication from an aircraft without subscribing to the Inmarsat service is more like a mobile phone talking to the cell tower without a valid SIM or blacklisted IMEI or like a phone with a valid SIM without a particular service feature. The latter would require the satellite to perform the subscriber validation for every aircraft flying even without the service for every contact or have it registered all the time like a cellular network, so I think it unlikely. Note that this is different situation from the case of a subscribed aircraft that has turned off a specific app like ACARS.

If the reported "ping" was based just on the "IMEI" from the aircraft equipment, it seems it would be much easier to spoof this from anywhere on the ground with sufficient transmission capability to reach the satellite than spoof the "IMSI" that is encrypted in a "SIM".

The telephony system doesn't worry too much about the IMEI being spoofed since no service is provided without a valid SIM and the mobile network isn't designed to identify the caller from the IMEI.

So, I wonder whether this identification of MH370 is based on the equivalent of the IMEI or IMSI. If the former, it raises the possibility that it was a spoofed decoy from a different time and location to throw the search off and we have no information whatsoever regarding how long it flew or where it went. Frightening indeed.