I've been battling with this very issue. You've got to worry about these things:
- Usage of a manufacturers trademark - i.e. Vought, Grumman, North American etc. This is not a good idea unless you have permission from the current holder of the trademark, and someone out there *does* still hold that trademark, no matter how old it is.
- Usage of a plane's name - i.e. Corsair: most American manufacturers have trademarked these, so again not a good idea. I don't know if non-American companies have the same business-minded approach to trademarks of plane names, (or the same 'cut throat' tenacity to sue) e.g. British planes like the Spitfire - unsure how safe that is to use.
- Usage of the plane's designation - i.e. F4U: this was owned by the military -> tax payer, and is therefore safe to use. Sometimes, especially with British planes (again, Spitfire) the designation may not be well-known enough to use.
- Usage of the plane's likeness - companies will tell you you cannot use their planes 'likeness' or image - i.e. anything that looks like the plane - bitmap, 3D model etc. I've been told this would never hold up in a court, but it is still a risk.
My advice (and this is what I've been told by others who have published aviation related games) is to stop contacting companies, and only use the plane designations.
I have never heard of any non-US companies worry about this sort of thing. In fact I have first hand experience that they are actually nice to deal with and accommodating / not interested in asking for money / suing you. However I do not know about the big EU company (Airbus) that owns pretty much 95% of French / German manufacturers trademarks. I have heard rumours that Russian manufacturers are carefree with this sort of thing.
This isn't legal advice, just what I have heard from others. Maybe pay a lawyer to discuss these points. Good luck!
Edited by xbattlestation, 02 July 2014 - 05:29 PM.