[Balto]

The answer of invisibility is :

1-either you dont have the mod of the plane the player is using
2-either you have the plane too BUT you do not have the COUNTRY the player is using

i mean where you select nationnality if you only have the usual country like :
none
german
finland
usaf
usmc
us navy

and not the new country like :
venezuela
croatia
argentine
peru
israel
syria
irak
iran
etc...

(fo example if the player is playing under PERU country markings and if you do not have the PERU markings (you need a mod that enables multiple new country ).