Invisible Aircraft online

[Kupsised]

Are now, but only recently started and this problem dates back from before we'd even considered using mods (it was only because every server that we played and was decently populated used them that we took them up). Like I said, used to happen a lot with FAF markings, and that was pre-mod. Seems to happen to my brother at random though. I had figured that it might be markings so have tried chaning to all of the default airforces to make it go away, and it doesn't change anything.