Question

[Pursuivant]

Originally Posted by KG26_Alpha

Its disabled by default due to international banning.

More to the point, the swastika is banned in several European countries, and displaying the swastika or other symbols of Nazism is considered to be in bad taste in many other parts of the world. Unless you're flying offline, be careful.

There was an option to enable swastika emblems for Finnish and Luftwaffe planes available in previous versions of IL2, but I'm not sure it's still available.
If it's still an option, you can enable it within the conf.ini.

Other than that, in addition to custom skins, there are add ons (MAT manager, various mods) which allow swastika logos to be displayed.