Its been talked about for over a year, but never addressed.
There is no simconnect way to get information about MSFS MP aircraft.
Its a sad state of affairs when we can see Vatsim & IVAO (and Potentially PE) Planes in maps within the sim, while the MSFS MP map is such a let down.
I get it - Asobo may have higher priority things to do, and cannot do it themselves, but at least provide the API so other Devs can.
Here we have an In game map, showing Vatsim Aircraft, their Fight Planes, their current data etc etc, but NO such equivalent thing for MSFS MP.
While there are programs like Flight Events , that can display this data, it can only do so so Pilots running the Flight Events addon, and then only display aircraft that are also using Flight Events.
If Asobo were to do this, one might expect it to be done by now, after over a year of it being requested, (even before release, during Alpha Testing).
To be blunt (and this is just the way it is) a 3rd party Dev could probably do a far better job than Asobo, who have limited resources, so please – Asobo, at least release an API so that Devs can develop such an App.
I am sure the LNM Dev is one that would like to include MSFS MP aircraft display into his product, but cannot because there is no MP API.
Imagine also flying in a MP Twitch stream, and being able to see all the planes around you on a MAP… would open up all sorts of fun possibilities, (ie Limited Stream Group ATC etc etc)
Give 3rd party devs the Tools, and it is amazing what they can come up with