The only way that you can ensure that everyone sees each others Aircraft correctly is;
You are ALL using the Default Aircraft.
You ALL have the
exact same downloaded aircraft in your Hangars.
If you decide to use a downloaded P51, then everyone else has to have the exact same P51 Aircraft downloaded Aircraft in their Hangars for your Aircraft to display correctly to everyone else, and the same applies to everyone else!
For that reason I always try to use only DEFAULT Aircraft in my Multiplayer flights!
It's the way Multiplayer was designed to work!
Always start off with your selected Aircraft, and try not to change them for something else, mid-flight!
Otherwise, what you see, is not necessarily what everyone else sees....

...!
Paul..G-BPLF ..FS 2004..FS Navigator... 8-)...!