You get it even if you are not using a cockpit. Say for instance, from a Jeep.
I think this effect is
more noticeable with Nvidia, which has been plagued with color banding problems for some time. The only way to fight it is with dithering in the program itself, so "they" say.
You can try several methods including those mentioned on
this page to try to eliminate banding, but it is usually created by a combination of the game (or any program), the OS, and your monitor or even cables.
(EDIT): Sorry, meant to say AMD cards don't have as much of this issue.